Prepare v0.2.0: bump README version, add CHANGELOG

README dependency snippets now reference 0.2.0; the status banner
flips from "early development" / "not yet published" to "first public
release". CHANGELOG.md documents every feature shipping in 0.2.0,
the four known divergences from edtf.js, and the two explicitly
deferred items (localized formatting, Ant / Ivy smoke test).

This is the last commit before tagging v0.2.0; the release workflow
will read the version from the tag and run mvn versions:set to
strip -SNAPSHOT before deploying.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jeffreyameyer

CHANGELOG.md

@@ -0,0 +1,69 @@
+# Changelog
+
+All notable changes to this project are documented here. The format is
+loosely based on [Keep a Changelog](https://keepachangelog.com/) and
+this project follows [Semantic Versioning](https://semver.org/).
+
+## [0.2.0] — 2026-04-23
+
+First public release on Maven Central. Covers EDTF Levels 0, 1, and most
+of Level 2.
+
+### Added
+
+- **Level 0** parsing: ISO 8601-1 dates, datetimes (minute, second, and
+  millisecond precision), centuries.
+- **Level 1** parsing: uncertain (`?`), approximate (`~`), and combined
+  (`%`) markers; `Y`-notation for five-or-more-digit years; seasons
+  (codes 21–24); intervals with bounded, open (`..`), and unknown
+  endpoints; `EdtfYear`, `EdtfSeason`, `Endpoint` sealed type, and
+  `EdtfInterval` types.
+- **Level 2** parsing: non-progressive partial X-mask patterns in any
+  YYYY/MM/DD position; sets (`[2020,2021]`) and lists
+  (`{2019..2021}`) including consecutive `start..end` members and
+  `earlier`/`later` markers; extended season codes 25–41
+  (hemispheric variants, quadrimesters, half-year divisions);
+  three-digit decade notation (`199`, `199?`); `Y`-notation
+  exponential (`Y1E5`) and significant-digits (`Y12345S3`) forms;
+  positional UA markers on individual date components
+  (`2020?-05~`, `?2020-%05`).
+- **Comparison and bounds**: `EdtfTemporal#compareTo`,
+  `EdtfTemporal#covers`, and `long`-millisecond `min` / `max` for every
+  supported type.
+- **Canonical serialization**: every type implements `toEdtfString()`
+  in a form that round-trips with edtf.js for the supported subset.
+- **Build and CI**: Maven build targeting Java 17 bytecode, JPMS
+  module descriptor, GitHub Actions CI matrix (Java 17 + 21), release
+  workflow that signs with GPG and publishes via Sonatype Central
+  Portal, Dependabot, issue and PR templates, Contributor Covenant
+  code of conduct, AI-assisted-development disclosure in
+  `ATTRIBUTION.md`.
+- **Test coverage**: 247 unit tests including a generated
+  parity-vector harness comparing against `edtf.js` v4.11.0 output.
+
+### Known deviations from edtf.js
+
+Documented in code on the affected types. Summary:
+
+- **Datetime canonical form** is normalised to UTC and full
+  millisecond precision (matching edtf.js's `toISOString` output);
+  the original timezone offset is preserved on the in-memory value
+  via `EdtfDate#timeZone()` but not emitted by `toEdtfString()`.
+- **Datetime atomicity**: minute, second, and millisecond precision
+  values report `min == max` (atomic instants), matching edtf.js.
+- **Season codes 21–24** use calendar-quarter bounds
+  (Q1=Jan–Mar, etc.) rather than meteorological seasons,
+  matching the upstream reference.
+- **Consecutive list members** report bounds spanning
+  `start.min..end.max` (semantically the full range). edtf.js
+  reports `start.max` for the upper bound, which we consider an
+  upstream bug and diverge from.
+
+### Deferred to a future release
+
+- Locale-aware formatting via `ResourceBundle` (canonical EDTF
+  rendering only at this release).
+- Ant/Ivy consumption smoke test against a real JOSM plugin
+  scaffold.
+
+[0.2.0]: https://github.com/OpenHistoricalMap/edtf-java/releases/tag/v0.2.0

README.md

@@ -7,7 +7,7 @@ Format (EDTF)][edtf] strings, per **ISO 8601-2:2019** (with Amendment 1,
 This is a port of the JavaScript library [edtf.js][edtf-js] to the JVM,
 targeting Java 17+ with zero runtime dependencies.
 
-> **Status**: Early development (0.1.0-SNAPSHOT). Not yet published to Maven
+> **Status**: First public release (0.2.0). Available on Maven
 > Central.
 
 ## Quick start
@@ -32,20 +32,20 @@ Once published:
 <dependency>
     <groupId>io.github.openhistoricalmap</groupId>
     <artifactId>edtf</artifactId>
-    <version>0.1.0</version>
+    <version>0.2.0</version>
 </dependency>
 ```
 
 ### Gradle
 
 ```groovy
-implementation 'io.github.openhistoricalmap:edtf:0.1.0'
+implementation 'io.github.openhistoricalmap:edtf:0.2.0'
 ```
 
 ### Ant + Ivy (JOSM plugins)
 
 ```xml
-<dependency org="io.github.openhistoricalmap" name="edtf" rev="0.1.0"/>
+<dependency org="io.github.openhistoricalmap" name="edtf" rev="0.2.0"/>
 ```
 
 ## EDTF coverage