How to Use a 24-Hour Clock
A 24-hour clock numbers the hours consecutively, starting from 00:00, or midnight, to 23:59 (11:59 p.m., according to a 12-hour clock). The 24-hour system has long been used in the U.S. military, in computer systems and in Europe, where it is often referred to as "railroad time."
Turn on the 24-hour clock. Enter the "time set" mode.
Adjust the time to match an accurate 12-hour or 24-hour clock. From 1:00 a.m. until 12:00 p.m., the times are set identically on both 12- and 24-hour clocks. The equivalent of 1 p.m. for a 24-hour clock would be 13:00, for 2 p.m., 14:00 and so on consecutively until 23:59 (11:59 p.m.). Midnight on a 24-hour clock would be 00:00, rather than 12:00 a.m.
Reference the clock by reading the hours on the left of the colon and the minutes on the right, just as you would with a 12-hour clock. For example, 08:15 on a 24-hour clock is 8:15 a.m. on a 12-hour clock.
"Translate" the time into the a.m./p.m. system if you wish. When the hour shows any number above 12, subtract 12 from it. Thus, a reading of 16:30 on a 24-hour clock would be 4:30 p.m. on a 12-hour clock.
- Set the hour change for daylight savings time just as you would on a 12-hour clock.
- The time from a 24-hour clock is often reported in hundreds of hours. For example, 18:00 is generally referred to as "eighteen hundred hours." Nine o'clock in the morning on a 24-hour clock is commonly described as "o-nine hundred hours."
- Some 24-hour clocks can be set automatically. Read the instructions for the specific clock model you are using to properly position and connect the clock with an available satellite.