In your DeskTime settings, each user can be set to a different timezone.
To change someone's timezone, please go to Settings → Team members → Edit → General → Team member details, select the correct timezone, and click Save general settings.
Remember that these kinds of settings can only be edited by the Company Owner, Company Administrator, or User Administrator!
You can also change the timezone for the whole company. In that case, go to Settings → Account → General → Account details. Or, you can change it for a specific team. Go to Settings → Teams → Click on the specific team → General → Team details
Please keep in mind that the timezone entered in the Team members section will override the timezone you enter in the Account settings.