>Why do you think she would not allow the entry of 24:00?

I think by 'normal' clock time the next time after 23:59 is 00:00. 24:00 is same as 00:00. There is not a time of 24:01 -- it would be confusing to see 24:00 and then 00:01 when the seconds ticked by... Time goes from 00:00 to 23:59 each day.