Sources and method
How the converter works out each answer, and the official sources behind the rules this site explains.
This page explains how the converter gets its answers, and where the rules on this site come from.
How the converter works
Every answer is worked out from the time you give it, never typed in by hand. A time is counted as minutes after midnight, from 0 (0000) to 1,440 (2400), and every way of writing it is made from that number: military time, standard time with AM or PM, the 24-hour clock with a colon, and the words it is said in.
The same rules run in two places: on our server, which writes each page, and in your browser, which answers as you type. Before every change goes live, both are tested against the same list of cases and against every minute of the day, written out and read back both ways, so the two can’t drift apart.
What the converter reads
- Military time with four digits (1730, 0930), three digits (930 is read as 0930) or one or two digits for a whole hour (17 is 1700, and 5 is read as 0500, with a note).
- Standard time with AM or PM, with or without the colon and the minutes (5:30 pm, 5:30PM, 530pm, 5 pm, 12 am).
- “Noon”, “midnight”, a trailing “hours” or “hrs”, and a Z or “Zulu” at the end, which marks Coordinated Universal Time (UTC).
- Seconds (17:30:15) are accepted; the answer is given to the minute.
When a time could be read two ways, such as 5:30 without AM or PM, the converter says how it read it and gives the other reading too.
Where the rules come from
The rules this site explains, for how military time is written and said, midnight, and the zone letters, come from these publications. We read each one ourselves; where we name a rule on a page, we name its source there too.
- U.S. Army: AR 25-50, Preparing and Managing Correspondence (2020), paragraph 1-26; ATP 6-02.70, Techniques for Spectrum Management Operations (2015), Appendix E; FM 5-0, Planning and Orders Production (2024), Appendix D.
- U.S. Navy: SECNAV M-5216.5, Correspondence Manual, March 2010 and June 2015 editions, chapter 2, paragraph 15; NAVEDTRA 14325, Basic Military Requirements (2002), chapter 3.
- U.S. Air Force: AFH 33-337, The Tongue and Quill (2015).
- Allied communications (Australia, Canada, New Zealand, the UK and the US): ACP 121(I), Communication Instructions General (2010), chapter 3 and its Annex A; ACP 125(G), Radiotelephone Procedures (2016).
- Federal Aviation Administration: Aeronautical Information Manual, paragraph 4-2-12.
- National Institute of Standards and Technology (NIST): “Times of Day FAQs”, “How is UTC(NIST) related to Coordinated Universal Time (UTC) International Atomic Time (TAI), Greenwich Mean Time (GMT), USNO time, GPS time and Zulu time?” and “Daylight Saving Time Rules”.
- U.S. Government Publishing Office: Style Manual (2016), section 12.9.
- U.S. Naval Observatory: “Universal Time”.
- The places in each time zone: the IANA Time Zone Database.
Read October 26 and 27, 2026.
Where the sources disagree
The official publications don’t all say the same thing. Where they differ, our pages say so instead of picking one:
- Midnight. NIST suggests 11:59 p.m. or 12:01 a.m., or else 0000 for the start of a day and 2400 for its end. The Army’s correspondence rules write 0001 to 2400 and another Army manual (ATP 6-02.70) 0000 to 2359. The Navy’s correspondence manual wrote 0001 to 2400 until 2015 and 0000 to 2359 since, while its training manual uses 0000 and 2400. Allied message rules avoid 2400 where they can and use 0000 only with a fraction of a minute.
- 12 a.m. and 12 p.m. NIST calls them ambiguous; the GPO Style Manual lists 12 a.m. for midnight and 12 p.m. for noon. This site follows most clocks: 12:00 AM is midnight and 12:00 PM is noon, always beside the military time.
- “Hours”. The Army and the Air Force say not to write it; spoken examples in the Allied radio rules and an Army manual include it.
- Local time. One Army manual (ATP 6-02.70) uses the letter J; the Army’s orders manual (FM 5-0) and Allied message rules use the local zone’s own letter.
- Half-hour zones. The Army adds an asterisk to the letter; Allied rules use both letters.
- What Z stands for. Allied message rules (ACP 121, 2010) and the Air Force’s Tongue and Quill pair Z with Greenwich Mean Time; NIST, the FAA and the Army’s ATP 6-02.70 say UTC. For everyday use the two are the same.
Mistakes
If something on this site is wrong, please tell us: Corrections explains how.