That would appear to simultaneously make checking equality of timestamps easy and make interpreting the timestamps murder.
If I’m reading the code correctly, and mtime here:
is the unaltered last modified time from the file system, then checking equality should be easy and reliable.
For display purposes, the user definitely has to play along to the extent of religiously updating the current local time in their camera on each transition between standard and daylight time and on each travel event to a different time zone.
Plus, the dates of transitions between standard and daylight time are not the same in all locales.
This is a tough task. You have my sympathy.