An analogue clock, a clock with hands, shows the numbers 1 through to 12. It is a 12-hour clock. The first 12 hours of the day, from midnight to midday, are called am. The next 12 hours, from midday ...

The Material Design team has an interesting blog post into what it calls the “24-hour Clock Design Challenge” that chronicles Google’s work creating a time picker for those that use a 24-hour format ...

I believe it's acceptable for midnight to be 24:00 -- though any time after midnight is 00:xx.

The article explores the historical roots and practical applications of the 12-hour and 24-hour time formats. Originating from ancient Egypt and Babylonia respectively, these systems offer distinct ...