As discussed in #51651 (comment), when a datetime object is created from unix timestamp, the timezone constructor argument is ignored as demonstrated in https://onlinephp.io/c/b07d1 and also mentioned in PHP documentation:

The $timezone parameter and the current timezone are ignored when the $datetime parameter either is a UNIX timestamp (e.g. @946684800) or specifies a timezone (e.g. 2010-01-28T15:00:00+02:00).

This change shouldn't break any existing logic, given the places where this time is used already include timezone in the date format string.

Changes in effect

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   Message       Trigger                              Next Run                   
  ------------- ------------------------------------ --------------------------- 
-  TestMessage   PeriodicalTrigger: every 2 seconds   2023-09-16T15:54:46+00:00  
+  TestMessage   PeriodicalTrigger: every 2 seconds   2023-09-16T18:54:46+03:00  
  ------------- ------------------------------------ ---------------------------