Yes, you can do it easily by clicking the gear button in the Timeframe section on the Home tab. Click “Add timeframe” and enter the necessary value into the field. For example, if you want to make a 6-hour timeframe, multiply it by 60 and enter 360. You can delete the unnecessary timeframes as well.
You can also make this list of timeframes default for your new projects by clicking the “Make default” button.