The system settings mentioned by Mostafa are in DV > Console > System Settings. Search for time zone and you find all the configs related to that.

Before setting something there, you should be sure about your data, because that setting will change your OAC behavior when dealing with dates and times. And if you have OAC users from multiple time zones, they all will be affected by that parameter that is global for the whole OAC.

If your data is correctly defined in your database, with a proper time zone define, there shouldn't be issues and setting the default time zone in OAC will do the job. If your data doesn't have a time zone in the database because there was an assumption of an implicit time zone, then setting the OAC default one will do the job without issues. Still, make sure about the quality of your data in the database, and if needed (multiple time zone involved in various sources in OAC), handle the time zone at the database level.