Chelsea Clock Patriot Deck ClockAs one of the country’s oldest clockmakers, we’re often asked about the differences between military time and standard or “civilian” time. More specifically, why does the US military operate on a 24-hour clock?

The answer is quite simple: efficiency. By noting or communicating the hour within a 24-hour day by that specific number, it eliminates any confusion between AM and PM.  So, for instance, 1:00AM is expressed as 0100 (O one hundred hours), while 1:00PM is expressed as 1300 (thirteen hundred hours).

Military and standard time both use minutes and seconds in exactly the same way (although military time is not expressed with a colon). For example, 1:05PM is expressed as 1305 hours. When converting from regular to military time and vice versa, the minutes and seconds do not change. Midnight is written as 2400 or 0000.

Military time is a very concise method of expressing time that is used not only by military personnel, but by several emergency services such as law enforcement officers, firefighters and emergency medical professionals. Many 24-hour military timepieces include both 24- and 12-hour markings for ease of use, as do our Patriot Deck and Radio Room Clocks.

Click here to learn more about Chelsea’s Military collection, including the Patriot Deck Clock and the Radio Room Clock