24-hour clock
The 24-hour clock was a method of measuring time based on the 24 hours of the Earth day. It ran from midnight to midnight, starting at 0 hundred and ending at 24 hundred. A hundred was another word for hour. This was the standard time notation aboard Federation starships of the 23rd and 24th centuries. ()

In 2254, on board the , Captain Christopher Pike wanted the reports at oh five hundred (05:00). ()

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Time