diff --git a/docs/Changelog.md b/docs/Changelog.md
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@@ -5,6 +5,7 @@ based on merged pull requests. Search GitHub issues and pull requests for smalle
 
 ## 2.6.0-SNAPSHOT (under development)
 
+- ISO-8601 date time for GTFS API itinerary responses [#5660](https://github.com/opentripplanner/OpenTripPlanner/pull/5660)
 [](AUTOMATIC_CHANGELOG_PLACEHOLDER_DO_NOT_REMOVE)
 
 ## 2.5.0 (2024-03-13)