bernardflach
I think you are talking about an option that was in very old versions of osTicket. We dropped that years ago. Nowadays it’s supposed to automatically detect the time change based on a combination of server and system settings. Although I will say that a few time zones (like Asia/Kolkata) are notoriously bad with osTicket and don’t work too well.
What is your server timezone, PHP timezone, database timezone, system Default Timezone, and Agent Profile Time Zone set to? Also, is it old tickets or both new and old tickets showing incorrect times?
Cheers.