[BUG] Timetable Data is not returned in ISO format when querying with the date parameter

[Suhas-13]

Describe the bug

When querying the API for a user's timetable on a specific date, the start_time / end_time is provided as a time string in the form HOUR:MINUTE instead of ISO format as described on the API documentation.

To Reproduce

Make a request for a users personal timetable with the date parameter supplied
Observe the start_time/end_time for each event in the response

Expected behavior
start_time/end_time to be in ISO format.