Convert 12-hour time to military time and back, with the spoken form, seconds after midnight and decimal hours.
Pick an hour, minutes and AM or PM. Midnight and noon are the two cases that trip people up, and both are handled here.
Military time
1530
3:30 PM is 15:30, spoken as fifteen thirty hours
Enter a 24-hour value with or without a colon. Both 1530 and 15:30 are accepted.
12-hour time
3:30 PM
15:30 is half past three in the afternoon
To convert 12-hour time to military time, add 12 to any PM hour and keep any AM hour as it is, then write the result as four digits with no colon, so 3:30 PM is 1530 and 7:05 AM is 0705. Two values break the pattern and account for most conversion errors: 12:00 AM is 0000, not 1200, and 12:00 PM is 1200, not 0000. Going the other way, subtract 12 from any hour of 13 or above and label it PM. The minutes are copied straight across in every single case and never change.
12 AM → 00 1 PM to 11 PM → add 12 (3:30 PM → 1530) 1 AM to 11 AM → 01 to 11 12 PM → 12 (12:15 PM → 1215) minutes are unchanged in every conversionA military time converter translates between the two ways of writing a time of day: the 12-hour clock, which counts to twelve twice and needs AM or PM to say which half you mean, and the 24-hour clock, which counts straight from 0000 to 2359 and needs no qualifier at all. The tool at the top of this page works in both directions and shows every form of the answer you are likely to be asked for.
The two tabs do the following:
1530), the civilian 24-hour form with a colon (15:30), the spoken form, the number of seconds after midnight, and the time as decimal hours. There is a button that fills in the current time if you just want to know what right now is in military time.1530 and 15:30 are accepted, and three-digit entries such as 730 are padded to 0730 automatically. You get the 12-hour reading with AM or PM, the spoken form, the part of day, and the same seconds and decimal figures.Everything runs in your browser. Nothing is uploaded and nothing is stored, and the page keeps working with the connection switched off. If you need to measure the gap between two military times rather than convert one, the Time Duration Calculator handles spans that cross midnight, and the Hours Calculator totals a set of shifts. For a whole week of punches recorded in 24-hour form, use the Time Card Calculator.
The rest of this page is the reference material: a complete hour-by-hour chart covering all twenty-four hours with the spoken form for each, the full set of NATO time zone letters from Alpha to Zulu with their UTC offsets, the difference between what the United States armed forces actually write and the civilian 24-hour clock the rest of the world uses, and a straight explanation of the 0000 against 2400 argument about when a day ends.
Four steps, about fifteen seconds. Both tabs update as you type, and both can show the working.
Use 12-hour to 24-hour when you have a time like 3:30 PM and need military time. Use 24-hour to 12-hour when someone has handed you 1530 or 0730 and you need it in plain English.
On the first tab choose the hour, the minutes and AM or PM. On the second tab type the four digits with or without a colon; 1530, 15:30 and 730 are all understood.
The large figure is the military form with no colon. Underneath, the result grid repeats it with a colon for civilian use, which is the form most software, rosters and railway timetables expect.
The same grid gives the spoken form for reading a time aloud, the seconds after midnight for sorting or database work, and the decimal hours figure that payroll systems ask for.
Check the hour selector before you trust the answer. The single most common mistake is entering a PM time while the selector still says AM, or the reverse. A twelve-hour error is easy to make and hard to spot afterwards, because 0700 and 1900 look equally plausible on a schedule. If the result surprises you, look at AM or PM first.
Four rules going one way, four coming back. Learn the two that involve the number twelve and the rest look after themselves.
12:00 AM to 12:59 AM → hour becomes 00 1:00 AM to 11:59 AM → hour unchanged, padded to 2 digits 12:00 PM to 12:59 PM → hour stays 12 1:00 PM to 11:59 PM → hour + 12 minutes → copied across, always
Written as a single expression, where h is the 12-hour hour from 1 to 12:
military hour = (h mod 12) + (12 if PM else 0)
The mod 12 is what turns 12 into 0. For an AM time that gives 12 AM the value 00, and for a PM time it gives 12 PM the value 0 + 12 = 12. Both edge cases fall out of the same line, which is why the calculator never gets them wrong even though people frequently do.
00:00 to 00:59 → 12 AM (add 12, take AM) 01:00 to 11:59 → same hour, AM 12:00 to 12:59 → 12 PM (hour unchanged) 13:00 to 23:59 → hour − 12, PM minutes → copied across, always
Written as one expression, where H is the 24-hour hour from 0 to 23:
12-hour value = ((H + 11) mod 12) + 1 meridiem = AM if H < 12 else PM
That expression maps 0 to 12, 1 to 1, 11 to 11, 12 to 12, 13 to 1 and 23 to 11, which is exactly the sequence a 12-hour clock face shows. Note that noon is the boundary: 12:00 is the first PM minute, and 11:59 is the last AM minute.
Once a time is in 24-hour form, two further quantities are one short step away, and both turn up constantly in timesheets, log files and spreadsheets.
seconds after midnight = (HH × 3600) + (MM × 60) decimal hours = HH + (MM ÷ 60) 1530 → (15 × 3600) + (30 × 60) = 54,000 + 1,800 = 55,800 s 1530 → 15 + (30 ÷ 60) = 15.50 decimal hours
Seconds after midnight is the form to use when you want to sort times, compare them, or subtract one from another without worrying about carrying. Decimal hours is the form payroll wants, and the Decimal Hours Converter covers that conversion in depth including the quarter-hour rounding most employers apply. If you are subtracting two military times to find a duration, convert both to seconds first, subtract, and add 86,400 to the end value if it is the smaller of the two because the span crosses midnight.
Military time is a clock reading, not a duration. A military time can never exceed 2359, because it names a moment within a day. A duration can be 36:00 or 250:00 because it measures a length. Mixing the two is the reason people occasionally write 2530 when they mean 0130 the following day. When you are adding hours to a military time and pass 2400, subtract 2400 and move to the next date.
All twenty-four hours, with the four-digit form, the colon form, how each is said aloud, and the seconds after midnight. This is the table people mean when they search for a military time chart.
| 12-hour clock | Military | 24-hour | Spoken aloud | Seconds after midnight |
|---|---|---|---|---|
| 12:00 AM midnight | 0000 | 00:00 | zero hundred hours | 0 |
| 1:00 AM | 0100 | 01:00 | zero one hundred hours | 3,600 |
| 2:00 AM | 0200 | 02:00 | zero two hundred hours | 7,200 |
| 3:00 AM | 0300 | 03:00 | zero three hundred hours | 10,800 |
| 4:00 AM | 0400 | 04:00 | zero four hundred hours | 14,400 |
| 5:00 AM | 0500 | 05:00 | zero five hundred hours | 18,000 |
| 6:00 AM | 0600 | 06:00 | zero six hundred hours | 21,600 |
| 7:00 AM | 0700 | 07:00 | zero seven hundred hours | 25,200 |
| 8:00 AM | 0800 | 08:00 | zero eight hundred hours | 28,800 |
| 9:00 AM | 0900 | 09:00 | zero nine hundred hours | 32,400 |
| 10:00 AM | 1000 | 10:00 | ten hundred hours | 36,000 |
| 11:00 AM | 1100 | 11:00 | eleven hundred hours | 39,600 |
| 12:00 PM noon | 1200 | 12:00 | twelve hundred hours | 43,200 |
| 1:00 PM | 1300 | 13:00 | thirteen hundred hours | 46,800 |
| 2:00 PM | 1400 | 14:00 | fourteen hundred hours | 50,400 |
| 3:00 PM | 1500 | 15:00 | fifteen hundred hours | 54,000 |
| 4:00 PM | 1600 | 16:00 | sixteen hundred hours | 57,600 |
| 5:00 PM | 1700 | 17:00 | seventeen hundred hours | 61,200 |
| 6:00 PM | 1800 | 18:00 | eighteen hundred hours | 64,800 |
| 7:00 PM | 1900 | 19:00 | nineteen hundred hours | 68,400 |
| 8:00 PM | 2000 | 20:00 | twenty hundred hours | 72,000 |
| 9:00 PM | 2100 | 21:00 | twenty-one hundred hours | 75,600 |
| 10:00 PM | 2200 | 22:00 | twenty-two hundred hours | 79,200 |
| 11:00 PM | 2300 | 23:00 | twenty-three hundred hours | 82,800 |
There is no 2400 row because 2400 and 0000 are the same instant, and the chart lists each hour once. The last military time of any day is 2359. The seconds column counts from midnight, so it is the value to use when subtracting one time from another; multiply the difference by nothing and divide by 3,600 to read it back as hours.
Most of the world runs on the 24-hour clock and calls it nothing in particular. North Americans call the same idea military time, which is close enough for everyday use but blurs a real distinction. What the United States armed forces write is a specific notation with rules the civilian version does not have, and the differences matter as soon as you read an operational document rather than a bus timetable.
| Feature | US military time | Civilian 24-hour clock |
|---|---|---|
| Separator | No colon: 1530 | Colon: 15:30 |
| Leading zero | Always: 0730 | Always: 07:30 |
| Time zone | A single letter is appended: 1530Z is 15:30 UTC, 1530R is 15:30 in UTC−5. | Stated separately, or written as a numeric offset such as 15:30+02:00. |
| Midnight | 0000, with 2400 sometimes used for the end of a day | 00:00 only |
| Spoken form | Digits are read individually, and on-the-hour times take "hundred hours". | Usually read like an ordinary number: "fifteen thirty". |
| Seconds | Rarely written; the four-digit form is the norm. | Written when needed: 15:30:45. |
| Full date stamp | 151530ZJUL26 | 2026-07-15T15:30:00Z |
| Where you meet it | US armed forces, allied NATO forces, and North American emergency services. | Most countries for everyday time, plus transport, healthcare and computing everywhere. |
The full date stamp in the military row is a date time group: two digits for the day of the month, four for the time, the zone letter, three letters for the month and two for the year. So 151530ZJUL26 reads as 15:30 UTC on 15 July 2026. The civilian equivalent is the ISO 8601 timestamp shown beside it, which most software produces by default.
The 24-hour clock is the written norm in most of the world, but the 12-hour clock has not gone anywhere. In everyday speech and writing it remains standard in the United States, Canada outside Quebec, the United Kingdom, Australia, New Zealand, Ireland, the Philippines, and much of South Asia including India, Pakistan and Bangladesh. Several of those places use both: British and Australian train timetables, broadcast schedules and official documents run on the 24-hour clock while people say "half past three" and write "3:30 pm" in a text message.
Canada is a good illustration of the split. Federal documents and Quebec generally use the 24-hour clock, English-speaking provinces mostly use the 12-hour clock in daily life, and transport schedules use 24-hour form throughout. That is precisely the environment in which a converter earns its keep, because a roster written as 1900 and a text message saying "seven" have to agree. If the two times are also in different regions, the Time Zone Converter handles the offset separately from the format.
Twenty-two of the twenty-four hours follow one simple rule. The hours built around the number twelve do not, and that is where almost every conversion error lives.
12:00 AM is 0000 and 12:00 PM is 1200. Midnight starts the day at zero. Noon keeps its twelve. Every other AM hour keeps its own number and every other PM hour gains twelve, which is why 12 feels backwards: it is the only hour where AM subtracts and PM leaves the number alone.
12:00 AM → 0000 12:00 PM → 1200 12:01 AM → 0001 12:01 PM → 1201 12:30 AM → 0030 12:30 PM → 1230 12:59 AM → 0059 12:59 PM → 1259The 12-hour clock has no zero. It runs 12, 1, 2 and up to 11, then starts again, so the hour numbered twelve is doing the job that a zero would do in any other counting system. The 24-hour clock does have a zero, and it uses it. When you convert, the hour labelled 12 AM has to become 00 because it is the first hour of the day, and the hour labelled 12 PM has to stay 12 because it is the thirteenth hour of the day counted from zero.
The abbreviations make it worse rather than better. AM stands for ante meridiem, before noon, and PM for post meridiem, after noon. Noon itself is neither before nor after noon, so 12:00 PM is a convention rather than a logical necessity, and the same is true of 12:00 AM for midnight. That is exactly why careful writing avoids both: an appointment card that says "12 noon" or a roster that says "0000" cannot be misread, while one that says "12:00 AM" gets misread constantly.
Both notations name the same instant, and that is the whole problem. Written as 0000 it is the first minute of a day. Written as 2400 it is the last instant of the previous day. A deadline of "0000 Friday" and a deadline of "2400 Friday" are twenty-four hours apart, even though a clock displaying either one would look identical for a moment.
The civilian 24-hour clock resolves this by allowing only 00:00. ISO 8601, the international standard behind almost every timestamp in software, treats 00:00 as the start of a day; older editions of the standard also permitted 24:00 as an alternative way of writing the end of a day, and modern practice has moved away from it. Military and legal writing has been slower to converge, which is why you still see 2400 on some forms and orders.
The practical fix used across aviation, healthcare, contracts and rostering is to avoid the boundary entirely. Write 2359 for the last minute of a day and 0001 for the first minute of the next. Nobody can misread either one, the ambiguity disappears, and the cost is a single minute that almost never matters. If you are calculating a span that runs to the end of a day, the Time Calculator and the Time Duration Calculator both treat the boundary as 24:00:00 of elapsed time, so a shift from 0000 to 2400 correctly returns 24 hours rather than zero.
Midnight belongs to the day that is starting, not the one that is ending. A shift running 2200 Monday to 0600 Tuesday finishes on Tuesday, and its midpoint 0000 is already Tuesday. Payroll systems that log the whole shift against Monday are recording the start date, which is a policy choice rather than a fact about the clock. Check which convention your employer uses before reconciling a time card that includes overnight work.
Writing 1530 is easy. Saying it in a way that a radio operator will hear correctly is a separate skill with its own conventions.
The governing idea is that speech should be unambiguous over a noisy channel. That pushes the spoken form towards individual digits, away from words that sound like other words, and towards a redundant marker at the end so a listener knows the number was a time rather than a quantity.
0730 is "zero seven thirty", not "seven thirty". The zero is what tells the listener this is a four-digit time and that the hour is in the morning. Some services say "oh" instead of "zero" in casual speech, but "zero" is the trained form.
1500 is "fifteen hundred", 0800 is "zero eight hundred". The word marks the two trailing zeros so they cannot be lost. It is never "fifteen thousand" and never "fifteen o'clock".
"Fifteen hundred hours" is standard for on-the-hour times. For times with minutes it is often dropped, so 1530 is usually just "fifteen thirty". Practice varies between services and between countries, and neither form is wrong.
| Written | Spoken | 12-hour | Why it is said that way |
|---|---|---|---|
| 0000 | zero hundred hours, or simply midnight | 12:00 AM | Two pairs of zeros. Many units say "midnight" outright to remove all doubt. |
| 0001 | zero zero zero one | 12:01 AM | Every digit is spoken because there is no round number to lean on. |
| 0030 | zero zero thirty | 12:30 AM | The hour pair is spoken digit by digit, the minute pair as a number. |
| 0100 | zero one hundred hours | 1:00 AM | Leading zero, then the hour, then "hundred" for the empty minutes. |
| 0705 | zero seven zero five | 7:05 AM | Minutes under ten keep their own zero, so the pair is not heard as "fifty". |
| 0730 | zero seven thirty | 7:30 AM | The classic example. The hour is a digit pair, the minutes are a number. |
| 1000 | ten hundred hours | 10:00 AM | From ten onward there is no leading zero to speak. |
| 1045 | ten forty-five | 10:45 AM | Both halves are ordinary numbers once the hour reaches ten. |
| 1200 | twelve hundred hours, or noon | 12:00 PM | Saying "noon" is common in the same way "midnight" is for 0000. |
| 1305 | thirteen zero five | 1:05 PM | The minute zero is spoken so 05 is not heard as 50. |
| 1500 | fifteen hundred hours | 3:00 PM | The most quoted example of the form in film and television. |
| 1530 | fifteen thirty | 3:30 PM | With minutes present the "hours" suffix is usually dropped. |
| 1800 | eighteen hundred hours | 6:00 PM | The single most searched military time value. |
| 2100 | twenty-one hundred hours | 9:00 PM | Hours above twenty are said as compound numbers. |
| 2359 | twenty-three fifty-nine | 11:59 PM | The last minute of the day, and the safe way to write a midnight deadline. |
When a time zone letter is attached the phonetic name is spoken after the time, so 1530Z is "fifteen thirty Zulu" and 0700R is "zero seven hundred Romeo". The letter is never spelled out as a letter, because single letters are the easiest thing to lose over a radio.
A day laid out on both scales at once, and the same mapping folded onto a single dial. Between them they answer most of the questions people bring to a conversion chart.
A military time is only half a statement until you know which zone it is in. The armed forces solve that by appending a single letter, and the letters run through the whole alphabet.
Z, spoken "Zulu", means UTC, and every other letter is a whole-hour offset from it. A runs from UTC+1 up to I at UTC+9, then K, L and M cover UTC+10, UTC+11 and UTC+12. Going the other way, N is UTC−1 and the sequence continues to Y at UTC−12. The letter J is deliberately skipped in that run: it is Juliett, and it means the observer's own local time, whatever that happens to be.
1530Z = 15:30 UTC A → I = UTC+1 to UTC+9 1530R = 10:30 in UTC−5 K, L, M = UTC+10, +11, +12 0800A = 08:00 in UTC+1 N → Y = UTC−1 to UTC−12 J = local time, no fixed offsetThe reason the system exists is that a message can be written in one place, transmitted through several others, and acted on somewhere else again. A time of 1530 on its own is meaningless in that chain. A time of 1530Z is a single unambiguous instant that everybody can convert into their own clock. Aviation does the same thing with the same letter: flight plans, weather reports and air traffic control all run on UTC, and pilots say "Zulu" for exactly this reason.
| Letter | Phonetic name | UTC offset | 1200Z becomes | Example region |
|---|---|---|---|---|
| A | Alpha | UTC+1 | 1300 | Central Europe, Lagos, Algiers |
| B | Bravo | UTC+2 | 1400 | Eastern Europe, Cairo, Johannesburg |
| C | Charlie | UTC+3 | 1500 | Moscow, Nairobi, Riyadh |
| D | Delta | UTC+4 | 1600 | Dubai, Baku, Mauritius |
| E | Echo | UTC+5 | 1700 | Karachi, Tashkent, Yekaterinburg |
| F | Foxtrot | UTC+6 | 1800 | Dhaka, Almaty, Omsk |
| G | Golf | UTC+7 | 1900 | Bangkok, Jakarta, Hanoi |
| H | Hotel | UTC+8 | 2000 | Beijing, Singapore, Perth |
| I | India | UTC+9 | 2100 | Tokyo, Seoul, Yakutsk |
| J | Juliett skipped | local time | local | The observer's own zone, wherever that is |
| K | Kilo | UTC+10 | 2200 | Brisbane, Guam, Vladivostok |
| L | Lima | UTC+11 | 2300 | Solomon Islands, New Caledonia |
| M | Mike | UTC+12 | 0000 next day | New Zealand standard time, Fiji |
| N | November | UTC−1 | 1100 | Azores, Cabo Verde |
| O | Oscar | UTC−2 | 1000 | South Georgia, mid-Atlantic |
| P | Papa | UTC−3 | 0900 | Buenos Aires, Montevideo |
| Q | Quebec | UTC−4 | 0800 | Atlantic time, Halifax, Santiago |
| R | Romeo | UTC−5 | 0700 | Eastern standard time, Toronto, New York |
| S | Sierra | UTC−6 | 0600 | Central standard time, Winnipeg, Chicago |
| T | Tango | UTC−7 | 0500 | Mountain standard time, Calgary, Denver |
| U | Uniform | UTC−8 | 0400 | Pacific standard time, Vancouver, Los Angeles |
| V | Victor | UTC−9 | 0300 | Alaska standard time |
| W | Whiskey | UTC−10 | 0200 | Hawaii, Tahiti |
| X | X-ray | UTC−11 | 0100 | American Samoa, Niue |
| Y | Yankee | UTC−12 | 0000 same day | Baker Island, the far side of the date line |
| Z | Zulu UTC | UTC+0 | 1200 | Greenwich, Iceland, and all aviation and naval operations |
Twenty-five letters carry an offset and J carries none, which is the whole alphabet accounted for. The offsets are whole hours only, so zones on a half-hour or quarter-hour offset such as India at UTC+5:30, Newfoundland at UTC−3:30 and Nepal at UTC+5:45 have no letter of their own. Daylight saving is not represented either: a letter names a fixed offset, so a place that shifts seasonally moves from one letter to its neighbour rather than keeping the same one. For real zones with real seasonal rules, use the Time Zone Converter.
The letter Z was allocated to the zero-offset zone because it is the natural label for the reference point, and the spoken name comes from the NATO phonetic alphabet, in which the word for Z is Zulu. The alphabet itself exists because single spoken letters are catastrophically easy to confuse: B, C, D, E, G, P, T, V and Z all rhyme in English, and M and N are close enough to be lost under noise. Replacing each letter with a distinct two-syllable or three-syllable word makes the channel far more robust.
The same reasoning explains why the letter is spoken after the time rather than before it. A listener hears the four digits, holds them, and then receives the zone that anchors them. If the zone came first it would be the part most likely to be clipped by a transmission starting, and the digits would be left floating.
Converting a Zulu time can change the date as well as the hour. 0200Z on Tuesday is 2100R on Monday, because subtracting five hours crosses back over midnight. When you convert a time with a zone letter, always convert the date at the same time. This is the single most common error in reading a date time group, and it is worth an extra ten seconds every time.
Only the hour is converted. The two minute digits are copied from one format to the other exactly as they stand, in every direction and at every hour of the day.
This is worth stating on its own because a surprising number of people try to convert the minutes too, usually by adding twelve to them or by turning them into a fraction. Neither is right. Both clocks divide the hour into the same sixty minutes and number them the same way from 00 to 59. The only thing that differs between the two formats is how the hour is labelled.
3:47 PM → hour 3 + 12 = 15, minutes 47 unchanged → 1547 6:05 AM → hour 6 padded = 06, minutes 05 unchanged → 0605 0922 → hour 09 is AM, minutes 22 unchanged → 9:22 AM
If you want the minutes as a fraction of an hour, that is a separate conversion and a different question. Forty-seven minutes is 0.783 of an hour, which is what a timesheet wants, and the Decimal Hours Converter or the Minutes to Hours converter will do it. Nothing about writing the time in military form requires it.
| Minutes past the hour | 6 AM hour | 6 PM hour | 11 AM hour | 11 PM hour |
|---|---|---|---|---|
| :00 | 0600 | 1800 | 1100 | 2300 |
| :05 | 0605 | 1805 | 1105 | 2305 |
| :07 | 0607 | 1807 | 1107 | 2307 |
| :10 | 0610 | 1810 | 1110 | 2310 |
| :15 | 0615 | 1815 | 1115 | 2315 |
| :20 | 0620 | 1820 | 1120 | 2320 |
| :25 | 0625 | 1825 | 1125 | 2325 |
| :30 | 0630 | 1830 | 1130 | 2330 |
| :35 | 0635 | 1835 | 1135 | 2335 |
| :40 | 0640 | 1840 | 1140 | 2340 |
| :45 | 0645 | 1845 | 1145 | 2345 |
| :50 | 0650 | 1850 | 1150 | 2350 |
| :55 | 0655 | 1855 | 1155 | 2355 |
| :59 | 0659 | 1859 | 1159 | 2359 |
Read any row across and the last two digits are identical in all four columns. That is the whole point of the table: the conversion touches the first two digits only. The 6 PM column is exactly the 6 AM column with 12 added to the hour, and the 11 PM column is the 11 AM column with 12 added.
A shortlist of the values that get searched for by name, with everything the converter would give you for each.
| Military | 12-hour | Spoken | Seconds after midnight | Decimal hours |
|---|---|---|---|---|
| 0000 | 12:00 AM | zero hundred hours (midnight) | 0 | 0.00 |
| 0600 | 6:00 AM | zero six hundred hours | 21,600 | 6.00 |
| 0630 | 6:30 AM | zero six thirty | 23,400 | 6.50 |
| 0700 | 7:00 AM | zero seven hundred hours | 25,200 | 7.00 |
| 0730 | 7:30 AM | zero seven thirty | 27,000 | 7.50 |
| 0800 | 8:00 AM | zero eight hundred hours | 28,800 | 8.00 |
| 0900 | 9:00 AM | zero nine hundred hours | 32,400 | 9.00 |
| 1000 | 10:00 AM | ten hundred hours | 36,000 | 10.00 |
| 1100 | 11:00 AM | eleven hundred hours | 39,600 | 11.00 |
| 1200 | 12:00 PM | twelve hundred hours (noon) | 43,200 | 12.00 |
| 1300 | 1:00 PM | thirteen hundred hours | 46,800 | 13.00 |
| 1400 | 2:00 PM | fourteen hundred hours | 50,400 | 14.00 |
| 1500 | 3:00 PM | fifteen hundred hours | 54,000 | 15.00 |
| 1600 | 4:00 PM | sixteen hundred hours | 57,600 | 16.00 |
| 1700 | 5:00 PM | seventeen hundred hours | 61,200 | 17.00 |
| 1730 | 5:30 PM | seventeen thirty | 63,000 | 17.50 |
| 1800 | 6:00 PM | eighteen hundred hours | 64,800 | 18.00 |
| 1900 | 7:00 PM | nineteen hundred hours | 68,400 | 19.00 |
| 2000 | 8:00 PM | twenty hundred hours | 72,000 | 20.00 |
| 2100 | 9:00 PM | twenty-one hundred hours | 75,600 | 21.00 |
| 2200 | 10:00 PM | twenty-two hundred hours | 79,200 | 22.00 |
| 2300 | 11:00 PM | twenty-three hundred hours | 82,800 | 23.00 |
| 2330 | 11:30 PM | twenty-three thirty | 84,600 | 23.50 |
| 2359 | 11:59 PM | twenty-three fifty-nine | 86,340 | 23.98 |
Decimal hours are given to two places. 2359 is 23 + 59 divided by 60, which is 23.9833 and rounds to 23.98. The seconds column always divides by 3,600 exactly for the whole hours, so 1800 is 64,800 seconds, and 64,800 divided by 3,600 is 18 exactly.
1800 is 6:00 PM. Take the 18, subtract 12, and you get 6 in the afternoon. It is spoken as "eighteen hundred hours" and is a common start time for evening duty, dinner and shift handovers.
1500 is 3:00 PM. 15 minus 12 is 3, and the day has passed noon, so it takes PM. Spoken as "fifteen hundred hours". Add thirty minutes and it becomes 1530, or half past three.
2000 is 8:00 PM. 20 minus 12 is 8. Spoken as "twenty hundred hours". The pattern holds all the way up: 2100 is 9 PM, 2200 is 10 PM and 2300 is 11 PM.
Each one can be checked against the converter above. The working is shown so you can compare it with your own method.
A roster says a briefing starts at 1800. What time should you turn up in ordinary language?
= 6:00 PM, spoken "eighteen hundred hours"
A flight departs at 12:45 AM. This is the case people convert wrongly more than any other.
= 0045, spoken "zero zero forty-five"
A lunch meeting is at 12:15 PM. The temptation is to add 12 and write 2415, which is not a valid time.
= 1215, spoken "twelve fifteen"
A night shift runs from 2200 to 0615. How long is it, and how does it appear on a timesheet?
= 8:15 on the clock, 8.25 decimal hours
A crew briefing is scheduled for 1430Z. You are in Toronto on eastern standard time, which is the Romeo zone.
= 0930R, which is 9:30 AM locally
A medication chart records a dose given at 2130 with the next one due eight hours later.
= 0530 the next morning, 5:30 AM
Every field on this list adopted the 24-hour clock for the same underlying reason: an AM or PM that goes missing is a twelve-hour error, and in these settings a twelve-hour error is expensive.
Orders, movement schedules and coordinated operations depend on times that cannot be misread and can be transmitted by voice. The four-digit form with a zone letter does both jobs at once.
Flight plans, weather reports, clearances and logbooks all run on UTC, written and spoken as Zulu. A flight that crosses four time zones has one clock everyone agrees on, which removes the offset arithmetic from the cockpit entirely.
Medication charts, observation rounds and handover notes are written in 24-hour form so that a dose recorded at 0800 can never be given again at 8 in the evening. Twelve-hour dosing intervals make the AM and PM distinction unusually dangerous.
Dispatch logs, incident timelines and radio traffic all use 24-hour time, because the record has to stand up afterwards. A call logged at 0230 is unambiguous in a way that "half two" never is.
Rail, coach, ferry and freight timetables use the 24-hour clock worldwide, including in countries where daily speech is firmly 12-hour. A departure printed as 1815 cannot be confused with one at 0615.
Running orders, rehearsal calls and live schedules are written in 24-hour form so that a cue at 1900 and a get-out at 2330 sit in obvious order on the same sheet.
Log files, databases and APIs store times in 24-hour form because it sorts correctly as text: 09:00 comes before 14:00 alphabetically as well as chronologically, which is untrue of "9:00 AM" and "2:00 PM".
Rosters are written in 24-hour form so that overnight shifts read in order rather than appearing to run backwards. Converting to decimal for pay comes afterwards, and a time card calculator handles both steps.
Anyone scheduling across borders ends up in 24-hour form, because half the participants come from countries where it is the norm. Pairing it with a fixed reference such as UTC removes the last of the ambiguity.
Six of these are twelve-hour errors, which is the worst kind because the result still looks like a plausible time.
| Mistake | What it looks like | The fix |
|---|---|---|
| Writing 12:00 AM as 1200 | midnight logged as noon | 12:00 AM is 0000. The error is exactly twelve hours and it is the most common one on this list. |
| Writing 12:30 PM as 0030 | half past noon logged as half past midnight | 12:30 PM is 1230. Noon is the only PM hour that keeps its number. |
| Adding 12 to a morning hour | 9:00 AM written as 2100 | AM hours from 1 to 11 keep their own number: 9:00 AM is 0900. |
| Dropping the leading zero | 7:30 AM written as 730 | Military time is always four digits: 0730. A three-digit value is ambiguous and looks like a quantity. |
| Converting the minutes too | 3:45 PM written as 1557 | Minutes are copied across untouched: 1545. Only the hour is converted. |
| Adding 12 in the wrong direction | 1300 read as 25:00 or 1:00 AM | Going from 24-hour to 12-hour you subtract 12. 1300 is 1:00 PM. |
| Treating 2400 as a new day | a task due 2400 Monday | 2400 Monday and 0000 Tuesday are the same instant. Write 2359 Monday or 0001 Tuesday. |
| Ignoring the zone letter | 1400Z acted on as 2:00 PM locally | Z is UTC, not your clock. In the Romeo zone, 1400Z is 0900R, five hours earlier. |
A quick self-check catches most of these: if the input said AM, the result must begin 00 through 11; if it said PM, the result must begin 12 through 23. Any four-digit result above 2359 or any three-digit result is wrong by construction.
The vocabulary you will meet on rosters, flight plans, medication charts and operational documents.
If you need to do arithmetic with the times rather than just convert them, the Time Calculator adds and subtracts durations, the Hours Calculator totals a set of start and finish times, and the Date Calculator handles spans that run across several days.
Direct answers to the questions people ask most about this calculation.
Military time is a way of writing the time of day as four digits running from 0000 to 2359, with no colon and no AM or PM. The first two digits are the hour counted from 0 to 23, and the last two are the minutes. Because each moment of the day has exactly one four-digit value, there is nothing to misread. In the United States armed forces a time zone letter is usually attached as well, so 1530Z means 15:30 UTC.
1800 is 6:00 PM. Subtract 12 from the hour: 18 minus 12 is 6, and because the value is above 12 the time is in the evening, so it takes PM. It is spoken as "eighteen hundred hours". The same rule gives 1900 as 7:00 PM, 2000 as 8:00 PM and 1700 as 5:00 PM.
Keep any AM hour as it is and pad it to two digits, and add 12 to any PM hour. So 7:05 AM is 0705 and 3:30 PM is 1530. The minutes are copied across unchanged in both cases. The two exceptions are the hours labelled 12: 12:00 AM becomes 0000 because midnight starts the day at zero, and 12:00 PM stays 1200 because noon keeps its twelve.
12:00 AM is 0000. It is midnight, the very start of the day, so the 24-hour clock numbers it zero. Writing it as 1200 puts it twelve hours out, in the middle of the day. If you find the label confusing, the safest habit is to write "midnight" or "0000" and avoid "12:00 AM" altogether, which is what most rosters and flight plans do.
12:00 PM is 1200. Noon is the only PM hour that does not gain twelve, because the hour is already 12 on both clocks. Adding 12 would give 2400, which is not a valid time of day and would name midnight instead. Every other PM hour does gain twelve, so 1:00 PM is 1300 and 11:00 PM is 2300.
Read the hour pair, then the minute pair, and say any leading zero. 0730 is "zero seven thirty". Times on the hour take the word hundred, so 1500 is "fifteen hundred hours" and 0800 is "zero eight hundred hours". Minutes below ten keep their own zero, so 1305 is "thirteen zero five". The word "hours" is usually dropped when minutes are present.
Z is the time zone letter for Coordinated Universal Time, spoken "Zulu". So 1530Z is 15:30 UTC, and everybody reading it converts to their own clock from that fixed point. Other letters mean other offsets: A is UTC+1, R is UTC minus 5 and M is UTC+12. The letter J means the reader's local time and has no fixed offset.
They express the same idea but the notation differs. The civilian 24-hour clock writes 15:30 with a colon and states the time zone separately or as a numeric offset. US military time writes 1530 with no colon and appends a single zone letter. Military documents also sometimes use 2400 for the end of a day, which the civilian standard does not allow.
Both notations point at the same instant, but they belong to different days: 0000 is the first minute of a day and 2400 is the end of the previous one. The civilian 24-hour clock permits only 00:00. To avoid the argument entirely, write 2359 for the end of a day and 0001 for the start of the next, which is standard practice in aviation, healthcare and contracts.
No. Only the hour is converted. Both clocks split the hour into the same sixty minutes numbered 00 to 59, so 3:47 PM becomes 1547 and 6:05 AM becomes 0605. If you are turning minutes into a fraction of an hour that is a different conversion, and 47 minutes is 0.783 decimal hours rather than anything to do with the military format.
2000 is 8:00 PM. Take the hour pair, 20, and subtract 12 to get 8, then label it PM because the value was above 12. It is spoken as "twenty hundred hours". The rest of the evening follows the same pattern: 2100 is 9:00 PM, 2200 is 10:00 PM, 2300 is 11:00 PM and 2359 is 11:59 PM.
Because a dosing error caused by a missing AM or PM is a twelve-hour error, and many medications are given on twelve-hour cycles. A chart entry of 0800 cannot be mistaken for the evening in the way that "8:00" can. The same reasoning applies to observation rounds, handover notes and anything that has to be reconstructed accurately from the record afterwards.
The 12-hour clock remains standard in everyday speech and informal writing in the United States, Canada outside Quebec, the United Kingdom, Ireland, Australia, New Zealand and the Philippines, and it is widely used across South Asia. Several of those places run both systems at once, with 24-hour time on timetables, official documents and broadcast schedules while people speak in 12-hour terms.
0000 is 12:00 AM, midnight, the first minute of a new day. One minute later is 0001, which is 12:01 AM, and one minute earlier is 2359, which is 11:59 PM on the previous day. Because 12:00 AM is so widely misread, many schedules simply write "midnight" or use 2359 and 0001 to sidestep the boundary.