Per the FIXME comment in https://gerrit.wikimedia.org/r/c/mediawiki/core/+/1175273/18/includes/json/ClockAdapter.php, we will want to update the wikimedia/timestamp Composer package in MediaWiki core to a version that includes the patch https://gerrit.wikimedia.org/r/c/mediawiki/libs/Timestamp/+/1180650, as part of the work on JWT tokens.
There have been some breaking changes merged since the last release, so this one will need to be a major version bump, to v5. There are other extensions and libraries that depend on v4: https://codesearch.wmcloud.org/search/?q=wikimedia%2Ftimestamp. We'll have to coordinate updating to the new version in anything deployed to WMF production.