1. AM/PM to 24 hours calculator

What is 12:21 AM in 24 hour notation and in military notation?

AM/PM to 24 hours converter

Change the values of the fields according to your desired time value:
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How to convert time from 12-hour clock to 24-hour clock and to military time

There are two main methods of displaying the time. The first one is the 12-hour clock which uses AM and PM, and the other is the 24-hour clock.

In 12-hour clock or 12-hour time notation the day is split into two 12-hour periods running from midnight (12:00 AM) to noon (12:00 PM), and noon to midnight.

In military time the day runs from midnight to midnight and is divided into 24 hours from 00:00 (midnight) to 23:59.

Military time or 12-hour military notation consists always of four digits. It starts at 0000, which corresponds to 12:00 AM. Thus, 12:00 AM = 0000 (subtract 12-hours). Thus, 12:15 AM = 0015, 12:30 AM = 0030 and so on. After 12:59 AM the 12-hour clock jumps to 1:00 AM = 0100 in military time. So, 1:30 AM = 0130, 9:30 AM = 0930, 11:20 AM = 1120, 12:59 PM = 1259 in military time. Within these intervals above the hours and minutes remain the same.

After and including 1:00 PM until 11:59 PM, you should add 12 to the hours to make the corresponding military time. For example: 2:00 PM = (2 + 12):00 = 1400, 5:30 PM = (5 + 12):30 = 1730, 11:59 PM = (11 + 12) = 2359 in military time.

After 23:59 PM the 12-hour clock turns to 12:00 AM which corresponds to midnight, at which point military time is reset to 0000 (the beginning of the day) and the process continues.

The math to convert from AM/PM (12-hour clock) to 24-hour clock is the same explained above for military time with small diferences in the way we write or spell the time. For example: 1:45 AM = 1:45, 10:35 AM = 10:35, 12:35 AM = 0:35, 3:33 PM = 15:33 in 24-hour time, and so on. Keep in mind that the 12-hour format is the one that appears on a actual watch that you wear on your wrist. So, if the hour value has only 1 digit, the clock shows only 1 digit.

When converting from AM/PM to military time or to 24-hour time, you just need to change the hour values while minute values remain the same.

Another way to understand time conversion from AM/PM to military time

From 12:00 AM to 12:59 AM, subtract 12 hours:

  • 12:00 AM = 0:00 = 0000 (midnight)
  • 12:15 AM = 0:15 = 0015
  • 12:30 AM = 0:30 = 0030

From 1:00 AM to 12:59 PM, the hours and minutes remain the same:

  • 9:00 AM = 9:00 = 0900
  • 10:30 AM = 10:30 = 1030
  • 9:45 AM = 9:45 = 0945
  • 12:00 AM = 12:00 = 1200 (noon)

From 1:00 PM to 11:59 PM, add 12 hours:

  • 1:15 PM = 13:15 = 1315
  • 3:17 PM = 15:17 = 1517
  • 10:15 PM = 1015

Some highlights or tips

The abbreviations AM and PM are from Latin:

  • AM: ante meridiem, before noon or before midday
  • PM: post meridiem, after noon or after midday

In military time hours are always "hundred", never "thousand", so

  • 1000 is "ten hundred" not "one thousand";
  • 2000 is "twenty hundred" not "two thousand".

12:00 AM = 00:00 = midnight; 12:00 PM = 12:00 = noon.

Midnight 00:00 and 24:00

In the 24-hour time notation, the day begins at midnight, 00:00. The notation 24:00 serves to refer to the end of a day. Physically, 24:00 of one day is the same time as 00:00 of the following day.

How to read military time - Chart with examples

12-hour Military Spelling
12:00 AM 0000 zero hundred hours
00:01 AM 0001 zero zero zero one hours
12:30 AM 0030 zero thirty hours
1:00 AM 0100 zero one hundred hours
1:30 AM 0130 zero one thirty hours
2:00 AM 0200 zero two hundred hours
2:15 AM 0215 zero two fifteen hours
3:00 AM 0300 zero three hundred hours
3:20 AM 0320 zero three twenty hours
3:45 AM 0345 zero three forty-five hours
4:00 AM 0400 zero four hundred hours
4:35 AM 0435 zero four thirty-five hours
5:00 AM 0500 zero five hundred hours
6:00 AM 0600 zero six hundred hours
7:00 AM 0700 zero seven hundred hours
8:00 AM 0800 zero eight hundred hours
9:00 AM 0900 zero nine hundred hours
10:00 AM 1000 ten hundred hours
11:00 AM 1100 eleven hundred hours
12:00 PM 1200 twelve hundred hours
1:00 PM 1300 thirteen hundred hours
2:00 PM 1400 fourteen hundred hours
3:00 PM 1500 fifteen hundred hours
4:00 PM 1600 sixteen hundred hours
5:00 PM 1700 seventeen hundred hours
6:00 PM 1800 eighteen hundred hours
7:00 PM 1900 nineteen hundred hours
8:00 PM 2000 twenty hundred hours
9:00 PM 2100 twenty-one hundred hours
10:00 PM 2200 twenty-two hundred hours
11:00 PM 2300 twenty-three hundred hours

Notes on reading military time

Whole hours are read "hundred hours". For example: 0200 is spelled "zero two hundred hours" or "oh two hundred hours", 0800 is spelled "oh eight hundred hours", 0905 = "oh nine oh five hours".

For times other than whole hours, the word hundred is omitted and oh or zero is used instead.

In the military time, the word "hours" is used after the numerals for time.

Sample Time Calculations

References