Your student wants to make a booking for two weeks on Sunday.
You tell them "I'm free all day and there are aircraft available most of the day".
They reply "How about 7.30am?"
The boss is right behind you and you have no reason to say no. It will be the night after your best mate's birthday...
Two weeks later you leave the Birthday party just as things are warming up. You arrive at the airport at 7.30am, have a coffee while waiting for the student. 8am passes by and you find their phone number in the records...
"Oh" they say, "I phoned up and cancelled that flight on Tuesday"