This setting is controlled by the account administrator is is located under Preferences > Preferences. You should set the appropriate time based on how your office works and processes payments and allow time for your staff to post them in InHANCE on your end. The time here is respective of your time zone.
We recommend setting Automatic Payments for early morning so that in the event there is a glitch (payment gateway is down, for example) there is time to take notice of that and adjust. This gives Transaction Warehouse some time during the day to assist in solving the problem and getting your Automatic Payments processed before the end of the day.