How can we have custom start times?

Hello,
We would like to have out start and finish hour times fixed - and customised.
This is for booking rooms during school hours - so the times would be..
8.50am - 9.30pm
9.30pm - 10.15am
10.15am - 11.00am
11.00am - 1pm
1pm-1.30pm
...etc...
Is this possible?
Happy to customise and hardcode if necessary
Paul