# CHANGELOG

0.2.29 (2026-06-20)
===================
This release adds support for [`defmt`], which is a highly efficient logging
framework that targets resource-constrained devices, like microcontrollers.

Enhancements:

* [#505](https://github.com/BurntSushi/jiff/issues/505):
Add support for the `defmt` crate by implementing `defmt::Format` on the
principle public types in Jiff.
* [#584](https://github.com/BurntSushi/jiff/pull/584):
Add `Zoned::UNIX_EPOCH` as a constant.
* [#587](https://github.com/BurntSushi/jiff/pull/587):
Change the `Debug` output for `civil::ISOWeekDate` to match the `Debug` output
style of other primitive datetime types.

Bug fixes:

* [#525](https://github.com/BurntSushi/jiff/issues/525):
Fix a bug that prevented time zone lookups when using an on-disk time zone
database on Windows.
* [#539](https://github.com/BurntSushi/jiff/issues/539):
Fix a bug where rendering a datetime in an error message would omit a `T`
separator.


0.2.28 (2026-05-28)
===================
This is a small release with a fix for test failures on 32-bit targets in
`no-alloc` environments.

Bug fixes:

* [#573](https://github.com/BurntSushi/jiff/issues/573):
Fix test failure on 32-bit targets in `no-alloc` environments.


0.2.27 (2026-05-26)
===================
This is a small release with a bug fix for build errors on Windows for very old
versions of Rust.

Bug fixes:

* [#566](https://github.com/BurntSushi/jiff/issues/566):
Fix build error on Windows for very old versions of Rust (e.g., 1.71).


0.2.26 (2026-05-25)
===================
This release has a couple enhancements.

Firstly, Jiff now uses `windows-link` for calling FFI routines on Windows
instead of `windows-sys`. Using `windows-link` means less churn and fewer
duplicates in the dependency graph.

Secondly, a new `jiff-sqlx 0.2.0` release has been put out to support
`sqlx 0.9.0`.

Enhancements:

* [#538](https://github.com/BurntSushi/jiff/pull/538):
Replace use of `windows-sys` with `windows-link` and inline bindings.
* [#561](https://github.com/BurntSushi/jiff/pull/561):
Update `jiff-sqlx` to use `sqlx 0.9.0` and release `jiff-sqlx 0.2.0`.

Bug fixes:

* [#548](https://github.com/BurntSushi/jiff/pull/548):
Absolutetize incorrect relative size terms in the documentation of `RoundMode`.


0.2.25 (2026-05-24)
===================
This release updates Jiff's bundled copy of the [IANA Time Zone Database]
to `2026b`. See the [`2026b` release announcement] for more details.

[`2026b` release announcement]: https://lists.iana.org//hyperkitty/list/tz-announce@iana.org/thread/VX2Z3CBO6KHTYZNBBKFFWM7ZCI6TVCXP/


0.2.24 (2026-04-23)
===================
This release primarily adds a new `memory_usage` routine for reporting
heap allocation sizes for the `TimeZone` and `Zoned` types. This
release also acknowledges and updates the timeline expectations for a
Jiff 1.0 release in `README.md`.

Enhancements:

* [#520](https://github.com/BurntSushi/jiff/issues/520):
Add `memory_usage` to the `TimeZone` and `Zoned` types.
* [#535](https://github.com/BurntSushi/jiff/pull/535):
Improve comment in `Span::checked_add` example.

Bug fixes:

* [#541](https://github.com/BurntSushi/jiff/pull/541):
Update Jiff 1.0 timeline.


0.2.23 (2026-03-03)
===================
This release updates Jiff's bundled copy of the [IANA Time Zone Database]
to `2026a`. See the [`2026a` release announcement] for more details.

[`2026a` release announcement]: https://lists.iana.org/hyperkitty/list/tz-announce@iana.org/thread/ASPLBE3A4BAEXIOQ3KZ6EJSJWBU6L53G/

0.2.22 (2026-02-28)
===================
This release includes a bug fix where fallible conversions from signed
durations to unsigned durations could panic in some cases.

Bug fixes:

* [#526](https://github.com/BurntSushi/jiff/issues/526):
Fix a panicking bug that occurs for
`std::time::Duration::try_from(SignedDuration::new(0, -1))`.


0.2.21 (2026-02-22)
===================
This release contains a performance improvement and a bug fix for
`civil::Date::new` where it could panic on some inputs.

Bug fixes:

* [#523](https://github.com/BurntSushi/jiff/issues/523):
Fix a bug where `Date::new` could panic. This was a regression introduced in
`jiff 0.2.20`.

Performance:

* [#518](https://github.com/BurntSushi/jiff/pull/518):
Improve `Timestamp` to `civil::DateTime` conversion performance by ~15%.


0.2.20 (2026-02-11)
===================
This release contains a major internal refactor that moves off of using ranged
integers internally. There are also some small bug fixes and added support for
finding the system time zone on emscripten targets.

Enhancements:

* [#11](https://github.com/BurntSushi/jiff/issues/11):
Stop using ranged integers internally.
* [#490](https://github.com/BurntSushi/jiff/issues/490):
Add support for retrieving the system time zone on emscripten targets.
* [#500](https://github.com/BurntSushi/jiff/issues/500):
Update comparison with the `time` crate in the Jiff documentation.
* [#502](https://github.com/BurntSushi/jiff/issues/502):
Enable some non-default features for the Rust Playground deployment.

Bug fixes:

* [#485](https://github.com/BurntSushi/jiff/issues/485):
Fix bug with padding for negative integers in `strftime`.
* [#486](https://github.com/BurntSushi/jiff/issues/486):
Make `%^c` result in uppercase strings where appropriate.


0.2.19 (2026-02-05)
===================
This is a small release with a performance optimization (with respect to doing
heavily contended arithmetic on `Zoned` values) and a bug fix for a panic
that can occur when using `%2s` in `strftime`.

Enhancements:

* [#491](https://github.com/BurntSushi/jiff/issues/491):
Avoid cloning `TimeZone` for consuming operations on `Zoned`.

Bug fixes:

* [#497](https://github.com/BurntSushi/jiff/issues/497):
Fix a panic in `timestamp.strftime("%2s")`.


0.2.18 (2026-01-05)
===================
This release ships a sizeable refactor to the RFC 2822, RFC 9110, RC
3339, RFC 9557, ISO 8601 and friendly format printers. Specifically,
they are now all monomorphic internally (instead of being generic over
`jiff::fmt::Write`) and write to uninitialized buffers. This improves
runtime performance (sometimes dramatically so), and to a more modest
degree, decreases binary size and improves compile times.

This release also includes a bug fix where `DateTime::MIN.to_zoned(..)`
could panic.

Enhancements:

* [#460](https://github.com/BurntSushi/jiff/pull/460):
Improve runtime performance and binary size of RFC 2822 printer.
* [#461](https://github.com/BurntSushi/jiff/pull/461):
Tweak behavior of printing min/max offsets in RFC 2822 and Temporal printers.
* [#462](https://github.com/BurntSushi/jiff/pull/462):
Export fallible constructors for `jiff::SignedDuration`.
* [#465](https://github.com/BurntSushi/jiff/pull/465):
Improve runtime performance and binary size of the "friendly" duration printer.
* [#468](https://github.com/BurntSushi/jiff/pull/468):
Improve runtime performance and binary size of the Temporal ISO 8601 duration
printer.
* [#470](https://github.com/BurntSushi/jiff/pull/470):
Improve runtime performance and binary size of the Temporal ISO 8601 datetime
printer.
* [#474](https://github.com/BurntSushi/jiff/pull/474):
Improve runtime performance and binary size of Jiff's `strftime`
implementation.
* [#477](https://github.com/BurntSushi/jiff/pull/477):
Fix a bug where time zone lookups for `civil::DateTime::MIN` could panic.


0.2.17 (2025-12-24)
===================
This release contains binary size improvements to Jiff, more succinct error
messages and some new minor APIs.

While Jiff 1.0 is overdue, I've been doing a lot of experimenting with
improving Jiff's binary size and compile times. In particular, I want to spend
time doing this before Jiff 1.0 so that we don't box ourselves into a corner.
(For example, some binary size improvements may require minor API breaking
changes.)

In this release, Jiff has switched to structured error handling internally
in an effort to provide error predicates and also hopefully improve binary
sizes and compile times. Overall this didn't have as big of an impact on
binary sizes or compile times as I was hoping. I did take this opportunity to
make Jiff's error messages a bit more succinct. In many cases, this involved
de-duplicating some aspects of error messages and omitting user provided input
in the messages. If you feel like there is a significant decrease in error
message quality that isn't easily amended by callers providing additional
context themselves, please open an issue.

This release also updates Jiff's bundled copy of the [IANA Time Zone Database]
to `2025c`. See the [`2025c` release announcement] for more details.

Enhancements:

* [#412](https://github.com/BurntSushi/jiff/issues/412):
Add `Display`, `FromStr`, `Serialize` and `Deserialize` trait implementations
for `jiff::civil::ISOWeekDate`. These all use the ISO 8601 week date format.
* [#418](https://github.com/BurntSushi/jiff/issues/418):
Add some basic predicates to `jiff::Error` for basic error introspection.
* [#453](https://github.com/BurntSushi/jiff/pull/453),
  [#454](https://github.com/BurntSushi/jiff/pull/454):
Switch to structured error handling internally.
* [#456](https://github.com/BurntSushi/jiff/pull/456),
  [#457](https://github.com/BurntSushi/jiff/pull/457),
  [#458](https://github.com/BurntSushi/jiff/pull/458):
Various improvements to binary size.

[`2025c` release announcement]: https://lists.iana.org/hyperkitty/list/tz-announce@iana.org/thread/TAGXKYLMAQRZRFTERQ33CEKOW7KRJVAK/


0.2.16 (2025-11-07)
===================
This release contains a number of enhancements and bug fixes that have accrued
over the last few months. Most are small polishes. A couple of the bug fixes
apply to panics that could occur when parsing invalid `TZ` strings or invalid
`strptime` format strings.

Also, parsing into a `Span` should now be much faster (for both the ISO 8601
and "friendly" duration formats).

Enhancements:

* [#298](https://github.com/BurntSushi/jiff/issues/298):
Add Serde helpers for (de)serializing `std::time::Duration` values.
* [#396](https://github.com/BurntSushi/jiff/issues/396):
Add `Sub` and `Add` trait implementations for `Zoned` (in addition to the
already existing trait implementations for `&Zoned`).
* [#397](https://github.com/BurntSushi/jiff/pull/397):
Add `BrokenDownTime::set_meridiem` and ensure it overrides the hour when
formatting.
* [#409](https://github.com/BurntSushi/jiff/pull/409):
Switch dependency on `serde` to `serde_core`. This should help speed up
compilation times in some cases.
* [#430](https://github.com/BurntSushi/jiff/pull/430):
Add new `Zoned::series` API, making it consistent with the same API on other
datetime types.
* [#432](https://github.com/BurntSushi/jiff/pull/432):
When `lenient` mode is enabled for `strftime`, Jiff will no longer error when
the formatting string contains invalid UTF-8.
* [#432](https://github.com/BurntSushi/jiff/pull/432):
Formatting of `%y` and `%g` no longer fails based on the specific year value.
* [#432](https://github.com/BurntSushi/jiff/pull/432):
Parsing of `%s` is now a bit more consistent with other fields. Moreover,
`BrokenDownTime::{to_timestamp,to_zoned}` will now prefer timestamps parsed
with `%s` over any other fields that have been parsed.
* [#433](https://github.com/BurntSushi/jiff/pull/433):
Allow parsing just a `%s` into a `Zoned` via the `Etc/Unknown` time zone.

Bug fixes:

* [#386](https://github.com/BurntSushi/jiff/issues/386):
Fix a bug where `2087-12-31T23:00:00Z` in the `Africa/Casablanca` time zone
could not be round-tripped (because its offset was calculated incorrectly as
a result of not handling "permanent DST" POSIX time zones).
* [#407](https://github.com/BurntSushi/jiff/issues/407):
Fix a panic that occurred when parsing an empty string as a POSIX time zone.
* [#410](https://github.com/BurntSushi/jiff/issues/410):
Fix a panic that could occur when parsing `%:` via `strptime` APIs.
* [#414](https://github.com/BurntSushi/jiff/pull/414):
Update some parts of the documentation to indicate that `TimeZone::unknown()`
is a fallback for `TimeZone::system()` (instead of the `jiff 0.1` behavior of
using `TimeZone::UTC`).
* [#423](https://github.com/BurntSushi/jiff/issues/423):
Fix a panicking bug when reading malformed TZif data.
* [#426](https://github.com/BurntSushi/jiff/issues/426):
Fix a panicking bug when parsing century (`%C`) via `strptime`.
* [#445](https://github.com/BurntSushi/jiff/pull/445):
Fixed bugs with parsing durations like `-9223372036854775808s`
and `-PT9223372036854775808S`.

Performance:

* [#445](https://github.com/BurntSushi/jiff/pull/445):
Parsing into `Span` or `SignedDuration` is now a fair bit faster in some cases.


0.2.15 (2025-06-13)
===================
This release fixes a bug where error values were being constructed during
parsing even in the success case. This was a regression introduced in `0.2.14`
as a result of trying to improve compilation times. Thankfully, fixing this
regression doesn't seem to meaningfully impact the amount of IR generated by
compiling Jiff.

Bug fixes:

* [#385](https://github.com/BurntSushi/jiff/pull/385):
Fixes a performance regression for parsing.


0.2.14 (2025-05-20)
===================
This release includes a smattering of bug fixes, and hopefully a small
improvement to the time it takes to compile Jiff. Also, in this release, when
`TZ` is set to a non-empty but invalid value, Jiff will always fall back to
`Etc/Unknown` when using `TimeZone::system()`. This differs from previous
behavior where Jiff would, in this case, attempt to read the system's default
time zone. This change brings Jiff into consistency with existing Unix tooling
like `date`, and is also arguably a better failure mode. That is, when `TZ` is
set but invalid, we shouldn't silently fall back to the default system time
zone, but instead do something that indicates something has potentially gone
wrong.

Enhancements:

* [#364](https://github.com/BurntSushi/jiff/issues/364):
Jiff now falls back to `Etc/Unknown` for invalid `TZ` values.
* [#379](https://github.com/BurntSushi/jiff/pull/379):
Improve compilation times.

Bug fixes:

* [#365](https://github.com/BurntSushi/jiff/issues/365):
Fixes a compile error in Jiff when only the `tzdb-concatenated` feature was
enabled.
* [#366](https://github.com/BurntSushi/jiff/issues/366):
Fixes slow initial `Zoned::now()` in environments where `/usr/share/zoneinfo`
is on a very slow file system (like CI environments).
* [#376](https://github.com/BurntSushi/jiff/issues/376):
Avoids searching for a tzdb at `/usr/share/zoneinfo` on Windows.


0.2.13 (2025-05-05)
===================
This release fixes a bug in a corner case where `TimeZone::following` could
sometimes omit the last time zone transition. This could only happen in time
zones that once had daylight saving time, but ended it. This did not have an
impact on other Jiff APIs that handle daylight saving time.

Bug fixes:

* [#362](https://github.com/BurntSushi/jiff/issues/362):
Fix a bug where `TimeZone::following` could omit the last historical time zone
transition.


0.2.12 (2025-05-03)
===================
This release fixes a couple bugs in Jiff's parser. In particular, a regression
was introduced in `jiff 0.2.11` where its RFC 2822 parser could panic on some
inputs. Previous releases of Jiff are unaffected.

Bug fixes:

* [#357](https://github.com/BurntSushi/jiff/issues/357):
Fix a bug where parsing `1970-06-01T00-00:45:00[Africa/Monrovia]` succeeded
but it should fail.
* [#359](https://github.com/BurntSushi/jiff/issues/359):
Fix a bug where the RFC 2822 parser could panic on some inputs.


0.2.11 (2025-05-01)
===================
This release includes new APIs for customizing Jiff's `strtime` behavior along
with a few minor bug fixes. Jiff's `strtime` formatting API has also been
optimized. It's about twice as fast as it was.

This release also coincides with the publication of `jiff-icu 0.2.0-beta.2`,
which has support for `icu 2.0.0-beta.2`.

Enhancements:

* [#338](https://github.com/BurntSushi/jiff/pull/338):
Add support for the `%c`, `%r`, `%X` and `%x` conversion specifiers.
* [#341](https://github.com/BurntSushi/jiff/issues/341):
Add support for `%q` in `jiff::fmt::strtime` (prints quarter of year).
* [#342](https://github.com/BurntSushi/jiff/issues/342):
Add support for `%::z` and `%:::z` in `jiff::fmt::strtime`.
* [#344](https://github.com/BurntSushi/jiff/issues/344):
Add support for `%N` in `jiff::fmt::strtime` (alias for `%9f`).
* [#350](https://github.com/BurntSushi/jiff/issues/350):
Add a "lenient" mode for `strtime` formatting APIs that ignores most errors.

Bug fixes:

* [#328](https://github.com/BurntSushi/jiff/issues/328):
Document default precision behavior of `Display` impls for datetime types.
* [#340](https://github.com/BurntSushi/jiff/issues/340):
Allow whitespace in more places in RFC 2822 parser (improves spec compliance).
* [#346](https://github.com/BurntSushi/jiff/issues/346):
`TimeZone::get("UTC")` should now always return `TimeZone::UTC`.

Performance:

* [#338](https://github.com/BurntSushi/jiff/pull/338):
Jiff's `strftime` APIs are now approximately twice as fast as they were.
Performance should be comparable to `chrono` and `time`'s prebuilt APIs.


0.2.10 (2025-04-21)
===================
This release includes a bug fix for parsing `Tuesday` when using `%A` via
Jiff's `strptime` APIs. Specifically, it would recognize `Tueday` instead of
`Tuesday`.

Bug fixes:

* [#333](https://github.com/BurntSushi/jiff/issues/333):
Fix typo in `strptime` parsing from `Tueday` to `Tuesday`.


0.2.9 (2025-04-19)
==================
This release includes a bug fix that, in debug mode, could result in datetime
types having different hashes for the same value. This could cause problems,
for example, if you are using datetimes as keys in a hash map. This problem
didn't exist when Jiff was compiled in release mode.

This release also improves the panic message shown when the `js` feature isn't
enabled and the current time is requested on `wasm32-unknown-unknown` targets.

Enhancements:

* [#296](https://github.com/BurntSushi/jiff/issues/296):
Provide a better panic message when `Zoned::now()` fails on WASM.

Bug fixes:

* [#330](https://github.com/BurntSushi/jiff/issues/330):
Fix bug where `Hash` on datetime types could yield different hash values for
the same underlying date/time.


0.2.8 (2025-04-13)
==================
This release fixes a bug where the constructors on `SignedDuration`
for floating point durations could panic (in debug mode) or produce
incorrect results (in release mode). This bug only impacts users of
the `try_from_secs_{f32,f64}` and `from_secs_{f32,f64}` methods on
`SignedDuration`.

Enhancements:

* [#326](https://github.com/BurntSushi/jiff/pull/326):
Add an alternate `Debug` impl for `SignedDuration` that only shows its second
and nanosecond components (while using only one component when the other is
zero).

Bug fixes:

* [#324](https://github.com/BurntSushi/jiff/issues/324):
Fix a bug that could produce a panic or incorrect results in
`SignedDuration::(try_)?from_secs_{f32,f64}`.


0.2.7 (2025-04-13)
==================
This release includes a bug fix that changes how an empty but set `TZ`
environment variable is interpreted (as indistinguishable from `TZ=UTC`).
This also includes a new enabled by default create feature, `perf-inline`,
which allows toggling Jiff's use of `inline(always)`. This may help improve
compile times or decrease binary size.

Enhancements:

* [#320](https://github.com/BurntSushi/jiff/pull/320):
Remove some internal uses of generics to mildly improve compile times.
* [#321](https://github.com/BurntSushi/jiff/pull/321):
Add `perf-inline` crate feature for controlling `inline(always)` annotations.

Bug fixes:

* [#311](https://github.com/BurntSushi/jiff/issues/311):
Make `TZ=` indistinguishable from `TZ=UTC`.


0.2.6 (2025-04-07)
==================
This release includes a few bug fixes and support for discovering the IANA Time
Zone Database automatically on Illumos.

Enhancements:

* [#315](https://github.com/BurntSushi/jiff/issues/315):
Add support for automatically finding the tzdb on Illumos.

Bug fixes:

* [#305](https://github.com/BurntSushi/jiff/issues/305):
Fixed `Zoned` rounding on days with DST time zone transitions.
* [#309](https://github.com/BurntSushi/jiff/issues/309):
Fixed bug where `TimeZone::preceding` could omit historical time zone
transitions for time zones that have eliminated DST in the present.
* [#312](https://github.com/BurntSushi/jiff/issues/312):
Fixed `nth_weekday_in_month`, where it would sometimes incorrectly return an
error.


0.2.5 (2025-03-22)
==================
This release updates Jiff's bundled copy of the [IANA Time Zone Database] to
`2025b`. See the [`2025b` release announcement] for more details.

Enhancements:

* [#300](https://github.com/BurntSushi/jiff/pull/300):
Update `jiff-tzdb` to `2025b`.

[`2025b` release announcement]: https://lists.iana.org/hyperkitty/list/tz-announce@iana.org/thread/6JVHNHLB6I2WAYTQ75L6KEPEQHFXAJK3/


0.2.4 (2025-03-10)
==================
This is another small release that fixes a problem where Jiff could break
builds if they relied on inference for integer comparisons. Specifically, Jiff
uses internal trait impls to make comparing its internal ranged integers
more convenient. But Rust the language has no concept of "internal" trait
impls, and thus this can impact type inference. If code was written in a way
that relies on a singular trait impl that is available, then adding Jiff to
the project can cause it to break.

This isn't arguably Jiff's fault per se, but since these trait impls were just
about internal convenience and not essential to Jiff's design, we adopt a
pragmatic approach and just remove them.

Bug fixes:

* [#293](https://github.com/BurntSushi/jiff/issues/293):
Remove internal trait impls that can cause breaks due to inference failures.


0.2.3 (2025-03-07)
==================
This is a small release that fixes a bug in the handling of POSIX time zones
in some cases. Specifically, the implementation of `Date::yesterday` was wrong
when the date was the first of the month. This was a regression introduced in
`0.2.2` and was not present in older releases. More test coverage has been
added.

Bug fixes:

* [#290](https://github.com/BurntSushi/jiff/issues/290):
Fix bug in implementation of `Date::yesterday`.


0.2.2 (2025-03-06)
==================
This release of Jiff includes a new opt-in proc macro for embedding a
`TimeZone` into your binary. Just enable Jiff's `static` feature, and this will
print the current time in the `America/New_York` time zone:

```rust
use jiff::{
    tz::{self, TimeZone},
    Timestamp,
};

fn main() {
    static TZ: TimeZone = tz::get!("America/New_York");
    let zdt = Timestamp::now().to_zoned(TZ.clone());
    println!("{zdt}");
}
```

This enables `TimeZone` to be meaningfully used in core-only environments,
even when dynamic memory allocation isn't available.

This release also features a number of performance improvements for time zone
lookups. In some cases, the improvement is significant (by an order of
magnitude).

Additionally, the IANA Time Zone Database embedded into `jiff-tzdb` now
uses "rearguard" semantics. This means that the boolean flag indicating
whether daylight saving time is active or not (only accessible via
`TimeZone::to_offset_info`) will respect the actual definition of
daylight saving time. (This is relevant, for example, for time zones like
`Europe/Dublin`, where their summer time is _legally_ known as their standard
time, but is in effect daylight saving time.)

Enhancements:

* [#256](https://github.com/BurntSushi/jiff/issues/256):
Add `tz::{get,include}` macros for time zone support in core-only environments.
* [#258](https://github.com/BurntSushi/jiff/issues/258):
Switch to `rearguard` tzdb data in `jiff-tzdb` and document it.
* [#259](https://github.com/BurntSushi/jiff/pull/259):
De-duplicate TZif data in `jiff-tzdb`.
* [#273](https://github.com/BurntSushi/jiff/issues/273):
Add "crate features" documentation to `jiff-sqlx` and `jiff-diesel`.
* [#277](https://github.com/BurntSushi/jiff/issues/277):
Document semver guarantee for error conditions on `Timestamp` constructors.
* [#277](https://github.com/BurntSushi/jiff/pull/287):
Greatly optimize time zone lookups (for both timestamps and civil datetimes).

Bug fixes:

* [#261](https://github.com/BurntSushi/jiff/issues/261):
Improve the documentation for `ZonedWith::nanosecond` and
`ZonedWith::subsec_nanosecond`.


0.2.1 (2025-02-16)
==================
This release includes a massive number of optimizations that significantly
improves performance in some cases. If you had a workload whose performance
with Jiff was underwhelming, please give it a try. I welcome questions via
[Discussions on GitHub].

This release also provides a new API, `Timestamp::constant`, for constructing
`Timestamp` values in a `const` context.

Enhancements:

* [#235](https://github.com/BurntSushi/jiff/discussions/235),
  [#255](https://github.com/BurntSushi/jiff/discussions/255),
  [#266](https://github.com/BurntSushi/jiff/pull/266):
A massive number of performance improvements. Jiff should now generally be
faster than `chrono` and `time`.
* [#263](https://github.com/BurntSushi/jiff/issues/263):
Add `Timestamp::constant` for constructing timestamps in `const` context.


0.2.0 (2025-02-10)
==================
This is a new semver incompatible release of Jiff. It contains several breaking
changes. I expect most users of Jiff to be able to upgrade without any changes.
The fundamental API organization of Jiff has not changed.

Some of the highlights of this release include reducing footguns and better
ecosystem integration.

For reducing footguns, APIs on `Span` will no longer implicitly assume that
days are always 24 hours long. And `Span` no longer implements `PartialEq` or
`Eq` (instead favoring `span.fieldwise()` to create a value that supports naive
fieldwise comparison). Moreover, when using `TimeZone::system()` (perhaps via
`Zoned::now()`), if the system time zone could not be detected, then a special
`Etc/Unknown` time zone will be used instead. This avoids erroring, but also
surfaces itself to make it clearer that something has (perhaps) gone wrong.

As for ecosystem integration, this release coincides with the publication
of the [`jiff-icu`], [`jiff-sqlx`] and [`jiff-diesel`] crates. `jiff-icu`
integrates with the [ICU4X project], and is now the recommended way to use
Jiff to work with non-Gregorian calendars or to localize datetimes for end
users. `jiff-sqlx` and `jiff-diesel` provide wrapper types that implement the
necessary traits to make it ergonomic to store and retrieve Jiff values in a
database using [SQLx] or [Diesel], respectively.

Unless something unexpected happens, my plan is for the next breaking change
release to be Jiff 1.0 in about 6 months. Once Jiff 1.0 is out, I plan to
commit to it indefinitely.

**BREAKING CHANGES**:

This is an exhaustive list of breaking changes. Changes with the bolded
**RUNTIME** prefix are changes that will not be caught by the Rust compiler.
That is, they are changes in runtime behavior.

* [#28](https://github.com/BurntSushi/jiff/issues/28):
The deprecated `intz` routines on `Zoned`, `Timestamp`, `civil::DateTime` and
`civil::Date` have been removed. You can use `in_tz` instead. This change was
made because many found the name `intz` to be unclear.
* [#32](https://github.com/BurntSushi/jiff/issues/32):
The `PartialEq` and `Eq` trait implementations on `Span` have been removed.
Ideally these shouldn't have been used, but if you do need them, please use
`Span::fieldwise` to create a `SpanFieldwise`, which does have the `PartialEq`
and `Eq` traits implemented. These were removed on `Span` itself because they
made it very easy to commit subtle bugs.
* [#36](https://github.com/BurntSushi/jiff/issues/36):
Turn panics during `Timestamp::saturing_add` into errors. Callers adding
spans that are known to contain units of hours or smaller are guaranteed that
this will not return an error.
* **RUNTIME** [#48](https://github.com/BurntSushi/jiff/issues/48):
On `Span` APIs, days are no longer silently assumed to always be 24 hours when
a relative datetime is not provided. Instead, to perform operations on units
of days or bigger, callers must either provide a relative date or opt into
invariant 24-hour days with `SpanRelativeTo::days_are_24_hours`. Shortcuts have
been added to the span builders. For example, `SpanTotal::days_are_24_hours`.
* **RUNTIME** [#147](https://github.com/BurntSushi/jiff/issues/147):
Change the behavior of the deprecated `%V` conversion specifier in
`jiff::fmt::strtime` from formatting an IANA time zone identifier to formatting
an ISO 8601 week number. To format an IANA time zone identifier, use `%Q` or
`%:Q` (which were introduced in `jiff 0.1`).
* **RUNTIME** [#212](https://github.com/BurntSushi/jiff/issues/212):
When parsing into a `Zoned` with a civil time corresponding to a gap, we treat
all offsets as invalid and return an error. Previously, we would accept the
offset as given. This brings us into line with Temporal's behavior. For
example, previously Jiff accepted `2006-04-02T02:30-05[America/Indiana/Vevay]`
but will now return an error. This is desirable for cases where a datetime in
the future is serialized before a change in the daylight saving time rules.
For more examples, see `jiff::fmt::temporal::DateTimeParser::offset_conflict`
for details on how to change Jiff's default behavior. This behavior change also
applies to `tz::OffsetConflict::PreferOffset`.
* **RUNTIME** [#213](https://github.com/BurntSushi/jiff/issues/213):
Tweak the semantics of `tz::TimeZoneDatabase` so that it only initializes one
internal tzdb instead of trying to find as many as possible. It is unlikely
that you'll be impacted by this change, but it's meant to make the semantics
be a bit more sensible. (In `jiff 0.1`, it was in theory possible for one tz
lookup to succeed in the system zoneinfo and then another tz lookup to fail
in zoneinfo but succeed automatically via the bundled copy. But this seems
confusing and possibly not desirable. Hence the change.)
* [#218](https://github.com/BurntSushi/jiff/issues/218):
In order to make naming a little more consistent between `Zoned`
and `civil::Date`, the `civil::Date::to_iso_week_date` and
`civil::ISOWeekDate::to_date` APIs were renamed to `civil::Date::iso_week_date`
and `civil::ISOWeekDate::date`.
* [#220](https://github.com/BurntSushi/jiff/issues/220):
Remove `Span::to_duration` for converting a `Span` to a `std::time::Duration`
and rename `Span::to_jiff_duration` to `Span::to_duration`. This prioritizes
`SignedDuration` as the "primary" non-calendar duration type in Jiff. And makes
it more consistent with APIs like `Zoned::duration_since`. For non-calendar
spans, the `TryFrom<Span> for std::time::Duration` still exists. For calendar
durations, use `Span::to_duration` and then convert the `SignedDuration` to
`std::time::Duration`. Additionally, `Timestamp::from_jiff_duration` and
`Timestamp::as_jiff_duration` were renamed to `Timestamp::from_duration` and
`Timestamp::as_duration`, respectively. The old deprecated routines on the
unsigned `std::time::Duration` have been removed.
* [#221](https://github.com/BurntSushi/jiff/issues/221):
Change the type of the value yielded by the `jiff::tz::TimeZoneNameIter`
iterator from `String` to `jiff::tz::TimeZoneName`. This opaque type is more
API evolution friendly. To access the string, either use `TimeZoneName`'s
`Display` trait implementation, or its `as_str` method.
* [#222](https://github.com/BurntSushi/jiff/issues/222):
Split `TimeZone::to_offset` into two methods. One that just returns the
offset, and another, `TimeZone::to_offset_info`, which includes the offset,
DST status and time zone abbreviation. The extra info is rarely needed and
is sometimes more costly to compute. Also, make the lifetime of the time
zone abbreviation returned by `TimeZoneTransition::abbreviation` tied to
the transition instead of the time zone (for future API flexibility, likely
in core-only environments). This change was overall motivated by wanting to
do less work in the common case (where we only need the offset), and for
reducing the size of a `TimeZone` considerably in core-only environments.
Callers previously using `TimeZone::to_offset` to get DST status and time zone
abbreviation should now use `TimeZone::to_offset_info`.
* **RUNTIME** [#230](https://github.com/BurntSushi/jiff/issues/230):
When `TimeZone::system()` cannot find a system configured time zone, `jiff
0.1` would automatically fall back to `TimeZone::UTC` (with a WARN-level log
message). In `jiff 0.2`, the fall back is now to `TimeZone::unknown()`, which
has a special `Etc/Unknown` identifier (as specified by Unicode and reserved by
the IANA time zone database). The fallback otherwise still behaves as if it
were `TimeZone::UTC`. This helps surface error conditions related to finding
the system time zone without causing unrecoverable failure.

Enhancements:

* [#136](https://github.com/BurntSushi/jiff/issues/136):
When the special `SpanRelativeTo::days_are_24_hours()` marker is used, weeks
will also be treated as invariant. That is, seven 24-hour days. In all cases,
working with years and months still requires a relative date.
* [#228](https://github.com/BurntSushi/jiff/issues/228):
It is now possible to forcefully use a bundled copy of the IANA time zone
database without relying on disabling crate features. This can be done by
enabling the `tzdb-bundle-always` crate feature and explicitly creating a
`jiff::tz::TimeZoneDatabase::bundled()` database. Once in hand, you must use
APIs like `TimeZoneDatabase::get` to create a `TimeZone` and avoid any APIs
that implicitly use the global time zone database (like `Timestamp::in_tz` or
even `Zoned::from_str`).
* [#238](https://github.com/BurntSushi/jiff/pull/238):
Add integration with the ICU4X project via the [`jiff-icu`] crate. `jiff-icu`
provides traits for easily converting between datetime types defined in Jiff
and datetime types defined in ICU4X.
* [#240](https://github.com/BurntSushi/jiff/pull/240):
Add integration with the SQLx project via the [`jiff-sqlx`] crate. `jiff-sqlx`
provides wrapper types that implement the necessary traits in SQLx for
reasonably ergonomic integration. This includes PostgreSQL and SQLite support,
but not MySQL support. (It's not clear if it's possible at present to provide
MySQL support for SQLx for datetime types outside of SQLx itself.)
* [#241](https://github.com/BurntSushi/jiff/pull/241):
Add integration with the Diesel project via the [`jiff-diesel`] crate.
`jiff-diesel` provides wrapper types that implement the necessary traits in
Diesel for reasonably ergonomic integration. This includes MySQL, PostgreSQL
and SQLite support.


0.1.29 (2025-02-02)
===================
This release includes a few small enhancements and a bug fix. In particular,
there is now Serde support for `TimeZone` and the `ISOWeekDate` API has been
filled out a bit more.

Unless a serious issue is uncovered, my plan is that this will be the last
release before `jiff 0.2`.

Enhancements:

* [#89](https://github.com/BurntSushi/jiff/issues/89):
Opt-in support for using Serde with `jiff::tz::TimeZone` has been added.
* [#227](https://github.com/BurntSushi/jiff/issues/227):
The `civil::ISOWeekDate` API has been beefed up with a few convenience methods.
* [#233](https://github.com/BurntSushi/jiff/issues/233):
Add `tz::Offset::round` for rounding time zone offsets.

Bug fixes:

* [#231](https://github.com/BurntSushi/jiff/issues/231):
Use more flexible offset equality when parsing offsets with fractional minutes.


0.1.28 (2025-01-27)
===================
This is a small release that just removes the dev-dependency on `serde_yml`.
It has been replaced with the deprecated `serde_yaml`. See
[this post about `serde_yml` shenanigans](https://x.com/davidtolnay/status/1883906113428676938)
for why this was done. Note that this was only a dev-dependency and thus doesn't
impact folks using Jiff.

Bug fixes:

* [#225](https://github.com/BurntSushi/jiff/pull/225):
Remove dependency on `serde_yml` in favor of `serde_yaml`.


0.1.27 (2025-01-25)
===================
This is a small release with a bug fix for precision loss in some cases when
doing arithmetic on `Timestamp` or `Zoned`.

Bug fixes:

* [#223](https://github.com/BurntSushi/jiff/issues/223):
Fix the check for fractional seconds before taking the fast path.


0.1.26 (2025-01-23)
===================
This is a small release with another deprecation and a new API for doing
prefix parsing via `strptime`. There's also a bug fix for a corner case
when dealing with daylight saving time gaps with the `Zoned::with` API.

Deprecations:

* [#210](https://github.com/BurntSushi/jiff/pull/210):
  Deprecate `ISOWeekDate::to_date` in favor of `ISOWeekDate::date`.

Enhancements:

* [#209](https://github.com/BurntSushi/jiff/issues/209):
  Add `fmt::strtime::BrokenDownTime::parse_prefix` for parsing only a prefix.

Bug fixes:

* [#211](https://github.com/BurntSushi/jiff/issues/211):
  Fix unintuitive behavior of `Zoned::with` when time falls in a DST gap.


0.1.25 (2025-01-21)
===================
This release contains a number of deprecations in preparation for a `jiff 0.2`
release. The deprecations are meant to facilitate a smoother transition. The
deprecations, when possible, come with new APIs that will permit users to write
forward compatible code that will work in both `jiff 0.1` and `jiff 0.2`.

This release also includes a handful of new conversion specifiers in Jiff's
`strftime` and `strptime` APIs. This improves compatibility with the analogous
implementation with GNU libc.

Deprecations:

* [#28](https://github.com/BurntSushi/jiff/issues/28):
The `intz` methods on `Zoned`, `Timestamp`, `civil::DateTime` and `civil::Date`
have been deprecated in favor of `in_tz`.
* [#32](https://github.com/BurntSushi/jiff/issues/32):
The `Eq` and `PartialEq` trait implementations on `Span` have been deprecated
in favor of using the new `SpanFieldwise` type.
* [#48](https://github.com/BurntSushi/jiff/issues/48):
Silently assuming days are always 24 hours in some `Span` APIs has now been
deprecated. This will become an error in `jiff 0.2`. To continue assuming
days are 24 hours without a relative reference date, you can use the new
`SpanRelativeTo::days_are_24_hours` API. In `jiff 0.1`, you'll seen a
WARN-level log message emitted if you're code will be broken by `jiff 0.2`.
* [#147](https://github.com/BurntSushi/jiff/issues/147):
Both `%V` and `%:V` have been deprecated in favor of `%Q` and `%:Q`. In
`jiff 0.2`, `%V` will correspond to the ISO 8601 week number and `%:V` will
result in an error. This change was made to improve compatibility with other
`strtime` implementations. `%V` and `%:V` continue to correspond to IANA
time zone identifiers in `jiff 0.1`, but using them for parsing or formatting
will result in a WARN-level deprecation message.

Enhancements:

* [#147](https://github.com/BurntSushi/jiff/issues/147):
Adds a number of new conversion specifiers to Jiff's `strftime` and
`strptime` APIs. Specifically, `%C`, `%G`, `%g`, `%j`, `%k`, `%l`, `%n`, `%R`,
`%s`, `%t`, `%U`, `%u`, `%W`, `%w`. Their behavior should match the
corresponding specifiers in GNU libc.


0.1.24 (2025-01-16)
===================
This release updates Jiff's bundled copy of the [IANA Time Zone Database] to
`2025a`. See the [`2025a` release announcement] for more details.

Enhancements:

* [#206](https://github.com/BurntSushi/jiff/pull/206):
Update `jiff-tzdb` to `2025a`.

[`2025a` release announcement]: https://lists.iana.org/hyperkitty/list/tz-announce@iana.org/thread/MWII7R3HMCEDNUCIYQKSSTYYR7UWK4OQ/


0.1.23 (2025-01-13)
===================
This release includes some bug fixes, particularly for compilation on
`aarch64-linux-android`. There are also some minor enhancements, such as making
`Zoned::iso_week_date` a convenience function for `civil::Date::iso_week_date`,
in line with similar functions.

My current plan is to make a reasonably quick transition to `jiff 0.2` with a
few pending breaking changes. I will be making some `jiff 0.1` releases with
deprecations in order to make the transition as smooth as possible. If all goes
well with `jiff 0.2`, then my plan is still to do a Jiff 1.0 release in the
Summer of 2025.

Deprecations:

* [#197](https://github.com/BurntSushi/jiff/discussions/197):
`Date::to_iso_week_date` has been deprecated in favor of `Date::iso_week_date`.

Enhancements:

* [#196](https://github.com/BurntSushi/jiff/discussions/196):
Improve ISO week date documentation regarding weekday offsets.
* [#197](https://github.com/BurntSushi/jiff/discussions/197):
Add `Zoned::iso_week_date`, `DateTime::iso_week_date` and
`Date::iso_week_date`.

Bug fixes:

* [#200](https://github.com/BurntSushi/jiff/issues/200):
Fix compilation failure on Android in a Termux shell.
* [#202](https://github.com/BurntSushi/jiff/pull/202):
Re-add license files to crate artifact.


0.1.22 (2025-01-12)
===================
This release adds support for Android. This support means that Jiff will
automatically read its special concatenated time zone database, and will
read the `persist.sys.timezone` property to determine the system's current
time zone.

See [PLATFORM] for more specific information about Android support.

Note that this release also removed all non-essential files (including tests
and test data) for the artifact uploaded to crates.io. If you need or want
these files, please open a new issue.

Enhancements:

* [#140](https://github.com/BurntSushi/jiff/issues/140):
Add support for the Android platform.


0.1.21 (2025-01-04)
===================
This release includes a new API for setting the unit designator label in a
friendly formatted duration for zero-length durations.

Enhancements:

* [#192](https://github.com/BurntSushi/jiff/issues/192):
Add option to the friendly printer for setting the unit when writing a
zero-length duration.


0.1.20 (2025-01-03)
===================
This release includes a new type, `Pieces`, in the `jiff::fmt::temporal`
sub-module. This exposes the individual components of a parsed Temporal
ISO 8601 datetime string. It allows users of Jiff to circumvent the checks
in the higher level parsing routines that prevent you from shooting yourself
in the foot.

For example, parsing into a `Zoned` will return an error for raw RFC 3339
timestamps like `2025-01-03T22:03-05` because there is no time zone annotation.
Without a time zone, Jiff cannot do time zone aware arithmetic and rounding.
Instead, such a datetime can only be parsed into a `Timestamp`. This lower
level `Pieces` API now permits users of Jiff to parse this string into its
component parts and assemble it into a `Zoned` if they so choose.

Enhancements:

* [#188](https://github.com/BurntSushi/jiff/issues/188):
Add `fmt::temporal::Pieces` for granular datetime parsing and formatting.


0.1.19 (2025-01-02)
===================
This releases includes a UTF-8 related bug fix and a few enhancements.

Firstly, a `Span`'s default `Display` implementation now writes uppercase
unit designator labels. That means you'll get `P1Y2M3DT4H5M6S` instead
of `P1y2m3dT4h5m6s` by default. You can restore previous behavior via
`jiff::fmt::temporal::SpanPrinter::lowercase`. This change was made to improve
interoperability.

Secondly, `SignedDuration` now supports rounding via `SignedDuration::round`.
Note that it only supports rounding time units (hours or smaller). In order to
round with calendar units, you'll still need to use a `Span`.

Enhancements:

* [#130](https://github.com/BurntSushi/jiff/issues/130):
Document value ranges for methods like `year`, `day`, `hour` and so on.
* [#187](https://github.com/BurntSushi/jiff/issues/187):
Add a rounding API (for time units only) on `SignedDuration`.
* [#190](https://github.com/BurntSushi/jiff/issues/190):
`Span` and `SignedDuration` now use uppercase unit designator labels in their
default ISO 8601 `Display` implementation.

Bug fixes:

* [#155](https://github.com/BurntSushi/jiff/issues/155):
Relax `strftime` format strings from ASCII-only to all of UTF-8.


0.1.18 (2024-12-31)
===================
This release includes a few minor enhancements. Namely, the ability to iterate
over time zone transitions (in the future or the past), and some improvements
to failure modes when `Timestamp` and `Span` arithmetic fails.

Enhancements:

* [#144](https://github.com/BurntSushi/jiff/issues/144):
Add APIs for iterating over the transitions of a time zone.
* [#145](https://github.com/BurntSushi/jiff/issues/145):
Improve docs and error messages around fallible `Timestamp` arithmetic.


0.1.17 (2024-12-31)
===================
This release enhances Jiff's support for `no_std` environments by making its
`alloc` feature optional. When `alloc` is disabled, only fixed offset time
zones are supported and error messages are significantly degraded. If you have
core-only use cases for Jiff, I'd love to hear about them on the issue tracker.

Enhancements:

* [#162](https://github.com/BurntSushi/jiff/issues/162):
Support platforms that do not have atomics in `std`.
* [#168](https://github.com/BurntSushi/jiff/issues/168):
Jiff now supports disabling the `alloc` feature, which enables core-only mode.
* [#169](https://github.com/BurntSushi/jiff/issues/169):
Add `TimeZone::to_fixed_offset` for accessing an invariant offset if possible.


0.1.16 (2024-12-26)
===================
This release includes a new `jiff::fmt::friendly` module for formatting and
parsing durations in a more human readable format than what ISO 8601 specifies.
ISO 8601 remains the "default" duration format in Jiff due to its widespread
support. Here are some examples:

```text
40d
40 days
1y1d
1yr 1d
3d4h59m
3 days, 4 hours, 59 minutes
3d 4h 59m
2h30m
2h 30m
1mo
1w
1 week
1w4d
1 wk 4 days
1m
0.0021s
0s
0d
0 days
3 mins 34s 123ms
3 mins 34.123 secs
3 mins 34,123s
1y1mo1d1h1m1.1s
1yr 1mo 1day 1hr 1min 1.1sec
1 year, 1 month, 1 day, 1 hour, 1 minute 1.1 seconds
1 year, 1 month, 1 day, 01:01:01.1
```

To quickly demonstrate this new feature, here's a simple CLI program using
Clap:

```ignore
use clap::Parser;
use jiff::{Span, Zoned};

#[derive(Parser, Debug)]
#[command(version, about, long_about = None)]
struct Args {
    duration: Span,
}

fn main() {
    let args = Args::parse();
    println!("adding duration to now: {}", &Zoned::now() + args.duration);
}
```

And running the program:

```text
$ cargo run -q -- '1 year, 2 months, 5 hours'
adding duration to now: 2026-02-26T18:58:22-05:00[America/New_York]
$ cargo run -q -- 'P1Y2MT5H'  # ISO 8601 durations are supported too!
adding duration to now: 2026-02-26T19:00:57-05:00[America/New_York]
```

With Jiff, you should no longer need to pull in crates like
[`humantime`](https://docs.rs/humantime) and
[`humantime-serde`](https://docs.rs/humantime-serde)
to accomplish a similar task.

While this new format doesn't support any kind of internationalization, the
prevalence of the `humantime` crate suggests there's a desire for something
like this. The "friendly" format is meant to service all the same use cases
as `humantime` does for durations, but in a way that doesn't let you shoot
yourself in the foot.

The new "friendly" format is now the default for the `Debug` implementations
of both `Span` and `SignedDuration`. It's also available via the "alternate"
`Display` implementations for `Span` and `SignedDuration` as well. Moreover,
the `FromStr` trait implementations for both `Span` and `SignedDuration` will
parse _both_ the ISO 8601 duration and this new "friendly" format. Finally,
when `serde` integration is enabled, the `Deserialize` implementations for
`SignedDuration` and `Span` also automatically parse either ISO 8601 or the
friendly format. For serialization, ISO 8601 remains the default, but the
`jiff::fmt::serde` module provides easy to use helpers to switch to the
friendly format.

The `jiff::fmt::friendly` module documentation provides many more details,
including a complete grammar for the format.

Enhancements:

* [#143](https://github.com/BurntSushi/jiff/pull/143):
Add `Hash` implementation for `Zoned` and `Timestamp`.

Bug fixes:

* [#60](https://github.com/BurntSushi/jiff/issues/60):
Use a better `Debug` output format for `SignedDuration` and `Span`.
* [#111](https://github.com/BurntSushi/jiff/issues/111):
Add a new "friendly" duration format.
* [#138](https://github.com/BurntSushi/jiff/issues/138):
Fix deserialization in `serde_yml` and `serde_yaml` crates.
* [#161](https://github.com/BurntSushi/jiff/pull/161):
Fix `serde` dependency configuration so that it builds in no-std mode.


0.1.15 (2024-11-30)
===================
This release fixes a bug where Jiff would sometimes fail to parse TZif files
(found, typically, in `/usr/share/zoneinfo` on Unix systems). This occurred
when the TZif file contained a time zone transition outside the range of Jiff's
`Timestamp` type (which is `-9999-01-01` to `9999-12-31`). The bug fix works by
clamping the out-of-range transitions to Jiff's supported range.

This bug only seems to occur in some environments where their TZif files
contain more extreme values than what is typically found.

Bug fixes:

* [#163](https://github.com/BurntSushi/jiff/issues/163):
Fix a bug where Jiff would fail to parse some TZif files.


0.1.14 (2024-11-01)
===================
This release introduces new APIs to the RFC 2822 printer that explicitly
print timestamps in a format strictly compatible with [RFC 9110].

Enhancements:

* [#151](https://github.com/BurntSushi/jiff/issues/151):
Add `rfc2822::DateTimePrinter::timestamp_to_rfc9110_string` method.


0.1.13 (2024-09-07)
===================
This release introduces a new `jiff::tz::TimeZone::try_system` API. It is like
`TimeZone::system`, but returns an error instead of an automatic fall back to
UTC when the system time zone could not be discovered.

This also includes an update to the bundled [IANA Time Zone Database] to the
`2024b` release in the `jiff-tzdb` crate. As a reminder, the bundled database
is not used or included on Unix platforms by default. See [PLATFORM] for more
details.

Enhancements:

* [#65](https://github.com/BurntSushi/jiff/issues/65):
Add `TimeZone::try_system` for fallibly determining the system's time zone.
* [#125](https://github.com/BurntSushi/jiff/pull/125):
Update to the `2024b` release of the [IANA Time Zone Database].


0.1.12 (2024-08-31)
===================
This release introduces some new minor APIs that support formatting
`Timestamp` values as RFC 3339 strings with a specific offset.

Previously, using the standard formatting routines that Jiff provides, it was
only possible to format a `Timestamp` using Zulu time. For example:

```rust
use jiff::Timestamp;

assert_eq!(
    Timestamp::UNIX_EPOCH.to_string(),
    "1970-01-01T00:00:00Z",
);
```

This is fine most use cases, but it can be useful on occasion to format
a `Timestamp` with a specific offset. While this isn't as expressive
as formatting a datetime with a time zone (e.g., with an IANA time
zone identifier), it may be useful in contexts where you just want to
"hint" at what a user's local time is. To that end, there is a new
`Timestamp::display_with_offset` method that makes this possible:

```rust
use jiff::{tz, Timestamp};

assert_eq!(
    Timestamp::UNIX_EPOCH.display_with_offset(tz::offset(-5)).to_string(),
    "1969-12-31T19:00:00-05:00",
);
```

A corresponding API was added to `jiff::fmt::temporal::DateTimePrinter` for
lower level use.

Moreover, this release also includes new convenience APIs on the Temporal and
RFC 2822 printer types for returning strings. For example, previously, if you
were using the RFC 2822 printer to format a `Timestamp`, you had to do this:

```rust
use jiff::{fmt::rfc2822::DateTimePrinter, Timestamp};

let mut buf = String::new();
DateTimePrinter::new().print_timestamp(&Timestamp::UNIX_EPOCH, &mut buf).unwrap();
assert_eq!(buf, "Thu, 1 Jan 1970 00:00:00 -0000");
```

But now you can just do this:

```rust
use jiff::{fmt::rfc2822::DateTimePrinter, Timestamp};

assert_eq!(
    DateTimePrinter::new().timestamp_to_string(&Timestamp::UNIX_EPOCH).unwrap(),
    "Thu, 1 Jan 1970 00:00:00 -0000",
);
```

Enhancements:

* [#122](https://github.com/BurntSushi/jiff/pull/122):
Support formatting `Timestamp` to an RFC 3339 string with a specific offset.


0.1.11 (2024-08-28)
===================
This release includes a few small enhancements that have been requested over
the last several weeks. The biggest enhancement is a new `jiff::fmt::serde`
sub-module. It provides convenience routines similar to Chrono's
`chrono::serde` sub-module for serializing and deserializing between a
`jiff::Timestamp` and an integer number of seconds, milliseconds, microseconds
or nanoseconds. For example:

```rust
use jiff::Timestamp;

#[derive(serde::Serialize, serde::Deserialize)]
struct Record {
    #[serde(with = "jiff::fmt::serde::timestamp::second::required")]
    timestamp: Timestamp,
}

let json = r#"{"timestamp":1517644800}"#;
let got: Record = serde_json::from_str(&json).unwrap();
assert_eq!(got.timestamp, Timestamp::from_second(1517644800).unwrap());
assert_eq!(serde_json::to_string(&got).unwrap(), json);
```

If you need to support optional timestamps via `Option<Timestamp>`, then use
`jiff::fmt::serde::timestamp::second::optional` instead. Similarly, if you
need to support milliseconds instead of seconds, then replace `second` with
`millisecond` in the module path.

Enhancements:

* [#78](https://github.com/BurntSushi/jiff/issues/78):
Add `BrokenDownTime::set_{offset,iana_time_zone}` APIs.
* [#93](https://github.com/BurntSushi/jiff/issues/93):
Add note about using `Timestamp::now().to_zoned()` instead of
`Zoned::now().with_time_zone()`.
* [#101](https://github.com/BurntSushi/jiff/issues/101):
Add new `jiff::fmt::serde` module for integration with integer timestamps.
* [#117](https://github.com/BurntSushi/jiff/pull/117):
Remove `unsafe` usage in `libm` functions (applicable only to no-std users).


0.1.10 (2024-08-23)
===================
This release features a small bug fix where Jiff will detect an IANA time
zone identifier in some cases where it wouldn't before. While Jiff would
previously read the symlink metadata on `/etc/localtime` by default to discover
the system configured time zone on Unix systems, it *wouldn't* do so when
`TZ=/etc/localtime`. There's really no reason not to, so this release of Jiff
is fixed to use symlink sniffing on file paths provided by the `TZ` environment
variable.

Bug fixes:

* [#113](https://github.com/BurntSushi/jiff/issues/113):
When `TZ=/etc/localtime`, use symlink metadata to detect IANA identifier.


0.1.9 (2024-08-23)
==================
This release introduces new options for controlling the precision
of fractional seconds when printing `Zoned`, `Timestamp`,
`civil::DateTime` or `civil::Time` values. This is principally exposed
via `jiff::fmt::temporal::DateTimePrinter::precision`, but it's also
available via the standard library's formatting machinery. For example,
if `zdt` is a `jiff::Zoned`, then `format!("{zdt:.6}")` will format
it into a string with microsecond precision, even if its fractional
component is zero.

Enhancements:

* [#92](https://github.com/BurntSushi/jiff/issues/92):
Support setting the precision of fractional seconds when printing datetimes.


0.1.8 (2024-08-19)
==================
This releases fixes a build error in Jiff's `alloc`-only configuration. This
regression was introduced in `jiff 0.1.6`.

Bug fixes:

* [#108](https://github.com/BurntSushi/jiff/issues/108):
Use `core::time::Duration` everywhere instead of `std::time::Duration`.


0.1.7 (2024-08-18)
==================
This release relaxes Jiff's dependency on `windows-sys` to include multiple
semver incompatible releases. The purpose of this relaxation is to enable
Jiff to work with different versions of `windows-sys` in the hopes that this
reduces the likelihood that multiple copies of `windows-sys` are included in
your dependency tree.

Dependencies:

* [#106](https://github.com/BurntSushi/jiff/pull/106):
Relax `windows-sys` dependency constraint to `>=0.52.0, <=0.59.*`.


0.1.6 (2024-08-18)
==================
This release includes a new top-level type, `SignedDuration`, that provides a
near exact replica of `std::time::Duration`, but signed. It is meant to provide
alternative APIs for working with durations at a lower level than what `Span`
provides, and to facilitate better integration with the standard library.

A `SignedDuration` has also been integrated with all of Jiff's datetime types.
For example, previously, `Zoned::checked_add` only accepted a concrete
`jiff::Span`. But now it accepts a `jiff::Span`, `jiff::SignedDuration` or even
a `std::time::Duration`. Moreover, all of the `until` and `since` APIs on
datetime types have been ported and copied to return `SignedDuration` under the
`duration_until` and `duration_since` names.

This marks an initial integration phase with `SignedDuration`. It is planned
to integrate it more with the datetime types. Currently, there are integrations
on `Timestamp` and `Span`, but more will be added in the future.

Overall, folks should still use `Span`. That is the intended default duration
type in Jiff and will continue to be. Users of Jiff may find `SignedDuration`
useful in contexts where speed is important or when one needs to integrate
with the standard library.

This release also includes a few related deprecations as the APIs involving
`std::time::Duration` are phased out in favor of `SignedDuration`.

Deprecations:

* `Timestamp::as_duration`: replaced with `as_jiff_duration`, which will be
renamed to `as_duration` in `jiff 0.2`.
* `Timestamp::from_duration`: replaced with `from_jiff_duration`, which will be
renamed to `from_duration` in `jiff 0.2`.
* `Timestamp::from_signed_duration`: replaced with `from_jiff_duration`.
* `Span::to_duration`: replaced with `to_jiff_duration`, which will be renamed
to `to_duration` in `jiff 0.2`.

Basically, all of the above APIs either accept or return a
`std::time::Duration`. To avoid breaking changes at this point, new methods
for `SignedDuration` were added. For example, `Timestamp::as_jiff_duration`.
In `jiff 0.2`, the above deprecated methods will be removed and replaced with
equivalent methods that accept or return a `SignedDuration` instead. Callers
can then convert between a `SignedDuration` and a `std::time::Duration` using
appropriate `TryFrom` trait implementations.

Enhancements:

* [#21](https://github.com/BurntSushi/jiff/issues/21):
Add new top-level `SignedDuration` type.
* [#90](https://github.com/BurntSushi/jiff/issues/90):
Improve error message when using `Span` with >=day units with a `Timestamp`.

Performance:

* [#104](https://github.com/BurntSushi/jiff/pull/104)
Optimize offset calculations in time zones without DST.
* [#105](https://github.com/BurntSushi/jiff/pull/105)
Optimize offset calculations for timestamps after last DST rule change.


0.1.5 (2024-08-09)
==================
This release includes some improvements and bug fixes, particularly for Jiff's
`strtime` APIs.

Enhancements:

* [#63](https://github.com/BurntSushi/jiff/issues/63):
Add link to original Chrono maintainer's commentary in `DESIGN.md`.
* [#75](https://github.com/BurntSushi/jiff/issues/75):
Add support for `%V` for formatting _and_ parsing IANA time zone identifiers.
* [#79](https://github.com/BurntSushi/jiff/pull/79):
Add `devcontainer.json` to support GitHub Codespaces.
* [#85](https://github.com/BurntSushi/jiff/pull/85):
Set correct ranges for internal tracking in return value of `days_in_month`.

Bug fixes:

* [#59](https://github.com/BurntSushi/jiff/issues/59):
Fixes a bug where some `Span`s could not be roundtripped through ISO 8601.
* [#71](https://github.com/BurntSushi/jiff/issues/71):
Tweak wording in documentation of "printf"-style API.
* [#73](https://github.com/BurntSushi/jiff/issues/73):
Make it so `%.Nf` only formats to `N` decimal places.
* [#77](https://github.com/BurntSushi/jiff/pull/77):
Disable optimizations when running tests.


0.1.4 (2024-08-01)
==================
This release includes a small improvement for `strptime` that permits
`%Y%m%d` to parse `20240730` correctly.

Enhancements:

* [#62](https://github.com/BurntSushi/jiff/issues/62):
Tweak `strptime` so that things like `%Y` aren't unceremoniously greedy.


0.1.3 (2024-07-30)
==================
This release features support for `wasm32-unknown-unknown`. That is, when
Jiff's new `js` crate feature is enabled, Jiff will automatically use
JavaScript APIs to determine the current time and time zone.

Enhancements:

* [#58](https://github.com/BurntSushi/jiff/pull/58):
Add WASM support and a new `PLATFORM.md` guide.


0.1.2 (2024-07-28)
==================
This release features a few new APIs that a need for arose while experimenting
with actually using Jiff in real projects. Namely, the `jiff::fmt::strtime`
module now has `%f` and `%.f` directives for parsing and formatting fractional
seconds. And both `jiff::fmt::rfc2822` and `jiff::fmt::strtime` now have
support for skipping weekday checks during parsing. (Previously, Jiff required
that an English weekday be consistent with the date parsed, and there was no
way to opt out. While this is still the default behavior, callers can disable
this check.)

Enhancements:

* [#52](https://github.com/BurntSushi/jiff/pull/52):
Improve documentation for `Span` getter methods.
* [#53](https://github.com/BurntSushi/jiff/pull/53):
Add support for skipping weekday checking when parsing datetimes.
* [#55](https://github.com/BurntSushi/jiff/pull/55):
Add support for fractional seconds in `jiff::fmt::strtime`.

Bug fixes:

* [#49](https://github.com/BurntSushi/jiff/pull/49):
Fix informational regex describing ISO 8601 format.
* [#51](https://github.com/BurntSushi/jiff/pull/51):
Explicitly allow new deny-by-default lint `ambiguous_negative_literals`.


0.1.1 (2024-07-25)
==================
This is a new semver compatible release. The principle addition are APIs for
converting between a `jiff::Span` and a `std::time::Duration`. Specifically,
there are now `TryFrom<Span> for Duration` and `TryFrom<Duration> for Span`
trait implementations. There is also a `Span::to_duration`, which requires a
relative date, for converting spans with non-uniform units (like months) to a
`Duration`.

Enhancements:

* [#21](https://github.com/BurntSushi/jiff/issues/21),
  [#40](https://github.com/BurntSushi/jiff/issues/40):
Adds APIs for converting between `Span` and `std::time::Duration`.

Bug fixes:

* [#36](https://github.com/BurntSushi/jiff/issues/36):
Saturating arithmetic for `Timestamp` panics with day-or-greater units.
* [#38](https://github.com/BurntSushi/jiff/issues/38):
Fix some bugs in the micro-benchmarks.
* [#39](https://github.com/BurntSushi/jiff/issues/39):
Document that the RFC 2822 parser is not technically fully spec compliant.


0.1.0 (2024-07-21)
==================
The initial release of Jiff.

[IANA Time Zone Database]: https://www.iana.org/time-zones
[PLATFORM]: PLATFORM.md
[RFC 9110]: https://datatracker.ietf.org/doc/html/rfc9110#section-5.6.7-15
[`jiff-icu`]: https://docs.rs/jiff-icu
[`jiff-sqlx`]: https://docs.rs/jiff-sqlx
[`jiff-diesel`]: https://docs.rs/jiff-diesel
[ICU4X project]: https://github.com/unicode-org/icu4x
[SQLx]: https://github.com/launchbadge/sqlx
[Diesel]: https://github.com/diesel-rs/diesel
[Discussions on GitHub]: https://github.com/BurntSushi/jiff/discussions
[`defmt`]: https://github.com/BurntSushi/jiff/issues/587
