Why I cannot save my preferred timing for Booking Config?

In Settings -> Organisation Configuration, under Booking Config, you need to make sure the time you enter in the fields follow bellow order:
earliest possible <earliest free <latest free <latest possible
Please note that time 23:00:00, 23:30, 23:59 is considered the last hours of a day, while 00:00:00, and 00:30:00 are considered the beginning hours of a day.