Update changelog

CHANGES.md

@@ -2,6 +2,10 @@
 
 ## __NEXT__
 
+### Major changes
+
+* curate format-dates: Raises an error if provided date field does not exist in records. [#1509][] (@joverlee521)
+
 ### Features
 
 * Added a new sub-command `augur curate apply-geolocation-rules` to apply user curated geolocation rules to the geolocation fields in a metadata file. Previously, this was available as a script within the nextstrain/ingest repo. [#1491][] (@victorlin)
@@ -15,13 +19,15 @@
 
 * filter: Improve speed of checking duplicates in metadata, especially for large files. [#1466][] (@victorlin)
 * curate: Stop adding double quotes to the metadata TSV output when field values have internal quotes. [#1493][] (@joverlee521)
+* curate format-dates: Mask empty date values as `XXXX-XX-XX` to represent unknown dates. [#1509][] (@joverlee521)
 
 [#1466]: https://github.com/nextstrain/augur/pull/1466
 [#1490]: https://github.com/nextstrain/augur/pull/1490
 [#1491]: https://github.com/nextstrain/augur/pull/1491
 [#1493]: https://github.com/nextstrain/augur/pull/1493
 [#1495]: https://github.com/nextstrain/augur/pull/1495
 [#1501]: https://github.com/nextstrain/augur/pull/1501
+[#1509]: https://github.com/nextstrain/augur/pull/1509
 
 ## 24.4.0 (15 May 2024)