[Merge] ~hyask/meta-release:skia/fix_wrong_timestamp into meta-release:main

[Łukasz Zemczak]

+1 on the checker code.

As for changing the dates of existing series: I guess it's fine, but can we check if those aren't actually used somewhere? I mean, normally I'd treat those as immutable and set in stone, especially if a series is already released (like noble). But possibly doesn't matter? Wonder how we can check that.
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https://code.launchpad.net/~hyask/meta-release/+git/meta-release/+merge/471699
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