Date Time
24-Hours Clock Calculator
Convert a 12-hour clock time to 24-hour format.
Free to use — no sign-up or login.
Result
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Pick a direction. 12-hour to 24-hour asks for an hour from 1 to 12, a minute, and AM or PM. 24-hour to 12-hour asks for an hour from 0 to 23 and a minute. The hour field rejects numbers outside that range.
To add hours onto a timestamp, use the Time Calculator. To read the same instant in another city, use the Timezone Offset Calculator.
Midnight is 00:00 and noon is 12:00
12:00 AM is 00:00, the start of the calendar day. 12:00 PM is 12:00, midday. 12:15 AM is 00:15, and 12:15 PM is 12:15. Those two hours are the ones a free-typed mode number usually gets wrong.
Afternoon hours add 12
From 1:00 PM through 11:59 PM, the 24-hour hour is the 12-hour hour plus 12. 2:30 PM is 14:30. The reverse takes 14:30 back to 2:30 PM. 0 and 13 are not valid 12-hour hours.
Worked example: 2:30 PM and 00:15
2:30 PM converts to 14:30. In the other direction, hour 0 and minute 15 convert to 12:15 AM. Hour 13 on the 12-hour side is rejected.
\[ 14{:}30 = 2{:}30\,\mathrm{PM} \]
Frequently asked questions
What is 12:00 AM in 24-hour time?
00:00. It is midnight at the start of the day, not 12:00.
What is 12:00 PM in 24-hour time?
12:00. Noon does not add another 12.
Why can’t I type 13 in the 12-hour hour?
A 12-hour clock only has hours 1 through 12. Thirteen belongs in the 24-hour direction.
What is 00:15 in 12-hour time?
12:15 AM.
Does this convert time zones?
No. It only changes how the same clock time is written.
References
Assumptions and limitations
This is a notation conversion for one clock time. It does not add hours, apply daylight saving, or name a city.