To assist with adding / editing class times, pre-defined time intervals can be set, so only relevant time options are displayed.
eg: Classes only occur at 15 minute intervals, so only :00, :15, :30 and :45 time options are required.
Customising this for your centre is very easy.
Go to: Configuration -> System Setup
Edit the entry for Schedule Interval(mins). For 5 minute intervals, enter 5 then save the settings.