One thing missing in the description is that there is a difference between hh:mm and HH:mm DateFormat for 24h format:hh:mm = 12hour format (6pm = 6:00)HH:mm = 24hour format (6pm =18:00)
If you select to show the timepicker to 24hour
Set the TimePicker24Hour to True. Check the following link for more info:
https://www.outsystems.com/forge/Component_Documentation.aspx?ProjectId=4196&ProjectName=date-time-picker-range