Definition:
A "twenty-four hour period" refers to the time it takes for the Earth to make a complete rotation on its axis, which is one full day. This period starts at midnight and ends at the next midnight, covering all the hours from 00:00 (12:00 AM) to 23:59 (11:59 PM).
A "twenty-four hour period" is a full day, from midnight to midnight. You can use it in various contexts, whether discussing schedules, events, or observations.