Military Time Converter

What Is Military Time?

The notation is the whole idea. A day contains twenty-four hours, so number them twenty-four ways and every reading of the clock becomes unique on its own — no suffix, no context, no second glance. The 12-hour dial does the opposite: it names each hour twice and then leans on two letters to say which of the two you meant.

The Four Digits, Read Left to Right

Two figures for the hour, two for the minutes, and leading zeros are compulsory — that is what keeps every time exactly four characters wide and sortable as a plain number. The FAA's Aeronautical Information Manual states the rule in one sentence: "The hour is indicated by the first two figures and the minutes by the last two figures." The day starts at 0000 and its last minute is 2359.

The colon is optional and regional rather than meaningful. US military and aviation practice writes 1730 closed up; a European departure board writes 17:30; a database writes 17:30:00. All three are the same four figures, and this converter reads the first two forms interchangeably.

Why Americans Call It Military Time

Where the 24-hour clock is the everyday civilian format, it needs no special name — it is simply the time. The label "military time" is an American one, and it exists because the United States is one of the places where the 12-hour clock stayed the civilian default — which leaves the armed forces, hospitals and aviation as the visible domestic users of the other system, and lends their name to it.

Machines settled the argument long ago. The W3C's profile of ISO 8601, the format most systems use to write timestamps, defines the time field as "two digits of hour (00 through 23)" and adds the parenthetical "am/pm NOT allowed". A log line, a calendar file and an airline schedule all use the 24-hour form for the same reason a medication chart does.

So the three names describe one clock in three costumes: military time when an American says it, the 24-hour clock when anyone else does, and ISO 8601 when a machine writes it down.

The Ambiguity It Removes

NIST puts the problem bluntly: "12 a.m. and 12 p.m. are ambiguous and should not be used." The reason is in the abbreviations themselves — a.m. and p.m. stand for ante meridiem and post meridiem, before noon and after noon. As NIST explains, "since noon is neither before noon nor after noon, a designation of either a.m. or p.m. is incorrect," and "midnight is both twelve hours before noon and twelve hours after noon."

Twenty-four-hour notation has nothing to resolve. Noon is 1200 and the midnight that opens a day is 0000, and neither number can be read as the other. That single property is why the clock spread into every field where a misread hour is expensive: an 0800 dose and a 2000 dose on the same chart cannot be confused, however tired the reader.

Where You Will Actually Meet It

• Aviation. The FAA "uses Coordinated Universal Time (UTC) for all operations", and the manual notes that "the term 'Zulu' may be used to denote UTC" — which is why an aviation time is written 1730Z rather than 5:30 PM.
• Healthcare. Medication administration records, observation charts and shift handovers are written in four digits so that 0800 and 2000 are twelve hours apart on the page as well as in the day.
• Transport. In much of the world, timetables and departure boards are written in 24-hour form, which is why a 17:30 train is never a 5:30 train.
• Emergency services, logistics and broadcast rundowns, where a shift or a slot has to be stated once and understood identically by everyone reading it.
• Computers. File timestamps, server logs and calendar files all store the hour as 00 through 23, and never store an AM/PM flag at all.

Shifts recorded as 0700 to 1530 still have to be turned into paid hours at the end of the week, and that is a separate piece of arithmetic handled by the Time Card Calculator.

How Do You Calculate Military Time?

Both directions apply one rule to the hour pair and leave the minute pair completely alone. Thirty minutes past an hour is thirty minutes past that hour in either notation, so every conversion on this page changes two digits and copies the other two.

The Military Time Formula

Those four lines collapse into two operations, and that is exactly how the code runs them. Divide the 24-hour figure by 12 and keep the remainder; if the remainder is 0, call it 12. Then the suffix is PM whenever the original hour was 12 or greater, and AM otherwise. Hour 0 gives a remainder of 0, so it becomes 12 with an AM suffix; hour 12 gives a remainder of 0 as well, so it becomes 12 with a PM suffix. The awkward noon-and-midnight pair falls out of the same two lines that handle every other hour.

24-hour → 12-hour (standard)
  hour 00        →  12, AM        0000 → 12:00 AM
  hours 01 to 11 →  hour, AM      0930 →  9:30 AM
  hour 12        →  12, PM        1200 → 12:00 PM
  hours 13 to 23 →  hour − 12, PM 1730 →  5:30 PM

12-hour → 24-hour (military)
  12 AM          →  00            12:15 AM → 0015
  1 to 11 AM     →  hour          7:45 AM  → 0745
  12 PM          →  12            12:15 PM → 1215
  1 to 11 PM     →  hour + 12     5:30 PM  → 1730

Minutes are carried across unchanged in every case.

Notice what is not in the formula: nothing multiplies, nothing rounds, and nothing depends on the minutes. Conversion here is relabeling, so it is exact — there is no version of this arithmetic that can be a minute out.

Step by Step: Military to Standard

• Split the four digits down the middle. 1730 becomes an hour of 17 and a minute of 30.
• Write the minutes down and forget about them — they are already finished.
• If the hour is 00, the answer is 12 and the suffix is AM. If the hour is 12, the answer is 12 and the suffix is PM.
• If the hour is 01 to 11, keep it as it is and add AM.
• If the hour is 13 to 23, subtract 12 and add PM. 17 − 12 = 5, so 1730 is 5:30 PM.

Only the last case involves any arithmetic, and it is the same subtraction every time. Half the day needs no calculation at all: 0930 is 9:30 AM by simply dropping the leading zero.

Step by Step: Standard to Military

• Take the hour and the AM/PM label separately. In 5:30 PM the hour is 5 and the label is PM.
• Copy the minutes across. They do not change.
• If the label is AM and the hour is 12, the hour becomes 00. Every other AM hour keeps its number.
• If the label is PM and the hour is 12, the hour stays 12.
• Every other PM hour gains 12. 5 + 12 = 17.
• Pad the result to four digits: hour 17 and minute 30 write as 1730; hour 7 and minute 45 write as 0745.

The padding step is the one people skip, and it is the one that makes the result sortable. 745 and 1730 do not line up in a column; 0745 and 1730 do, which is the property that makes 24-hour times usable in a roster or a spreadsheet.

Worked Example: 1730

The hour is 17, which is 13 or more, so it loses 12 and gains a PM. 17 − 12 = 5. The minutes were 30 before the conversion and they are 30 after it. That gives 5:30 PM, and it is the example the page opens with, because 1730 is already sitting in the time box when the page loads.

Calculator output — Military → Standard, 1730

5:30 PM · 1730 = 5:30 PM · Spoken: “1730 hours” · No AM/PM ambiguity — that is the whole point of the 24-hour clock

Run it backwards and the converter returns 1730 as its headline, with the middle line written as "5:30 PM = 17:30 in 24-hour time". Read those two outputs side by side and you can see a small habit of the notation: the headline drops the colon, the way a military or aviation document would, while the explanatory line puts it back, the way a timetable would. Both are the same time.

The Minutes Never Change

This is the part that gets over-thought. Whatever happens to the hour, the minute pair is transcribed. That is why times sharing a minute value stay paired across the whole day, and why the twelve-hour twins — two times exactly twelve hours apart — differ by 12 in the hour pair and by nothing at all in the minute pair.

In the 12-hour column of that table, each pair is separated by two letters and nothing else. In the military column they are separated by 1200 — a difference you can see without reading a suffix, which is the practical argument for the whole system.

The Two Times the ±12 Rule Breaks

Twelve o'clock is where the simple rule fails in both directions, and it fails because the 12-hour clock counts 12, 1, 2 rather than 0, 1, 2. Adding 12 to 12 PM would give 24; subtracting 12 from 1200 would give 0000. Neither is right. The correct answers are that 12:00 AM is 0000, 12:00 PM is 1200, and both are special-cased rather than calculated.

The converter marks them for you. Feed it 0000 and its last line reads "0000 is midnight — the day's first minute"; feed it 1200 and the line becomes "1200 is noon — no AM/PM ambiguity in 24-hour time". Every other hour of the day gets the generic line instead. Those notes also cover the minutes around them, so 0045 and 1201 carry the midnight and noon notes respectively.

This is the case NIST is warning about when it says the two 12 o'clock labels should not be used at all. If a document has to be unambiguous and is stuck in 12-hour notation, the usual workaround is to write "noon" and "midnight" as words, or to move the boundary to 11:59 PM or 12:01 AM where no ambiguity exists.

Military Time Chart

Every row below was produced by running this converter, not typed by hand. The first chart is the one people mean by "military time chart": the whole day, hour by hour, with the morning half on the left and the afternoon half on the right. Any row's two halves are exactly twelve hours apart.

Military Time Chart: Every Hour From 0000 to 2300

The left-hand column needs no arithmetic — strip the leading zero and you have the AM hour, with 0000 as the single exception that becomes 12. The right-hand column is the one worth memorizing, and there is nothing in it but the same subtraction of 12, repeated twelve times.

Standard Time to Military Time

The same day read from the other side, for when you have an AM/PM time in hand and need the four-digit form.

Read the AM column downward and the military form is just the same number padded to four digits — until you reach the top of it, where 12:00 AM becomes 0000 rather than the 1200 that pattern would predict. That one row is the whole difficulty of this direction.

Times With Minutes, and the Spoken Line

Whole hours are the easy half of a chart. These are times as they actually appear on a roster, together with the exact text the converter prints on its Spoken line for each one.

Whole hours are printed differently — 0600 comes back as “zero six hundred hours” and 1800 as “18 hundred hours” — and the reason for that split, along with the two competing ways people actually say these times out loud, is set out under How to Read Your Result below.

Military Time Examples Worked in Full

Five conversions that come up constantly. Each one was run through the converter, and the output below is the panel's own wording, with dots standing in for the places where it starts a new row.

0600: a Morning Hour, Untouched by Arithmetic

An hour below 12 needs no subtraction and no thought. Strip the leading zero, add AM, keep the minutes.

Calculator output — Military → Standard, 0600

6:00 AM · 0600 = 6:00 AM · Spoken: “zero six hundred hours” · No AM/PM ambiguity — that is the whole point of the 24-hour clock

The spoken form here is the one people recognize from films, and it is spelled out because the hour is a single digit. From hour 10 onward the converter prints the number instead: 1800 returns “18 hundred hours” rather than “eighteen hundred hours”, and any time carrying minutes comes back as its four digits plus the word hours.

2145: an Evening Time With Minutes

The hour is 21, so it loses 12 and becomes 9 PM. The 45 is transcribed. Nothing else happens.

Calculator output — Military → Standard, 2145

9:45 PM · 2145 = 9:45 PM · Spoken: “2145 hours” · No AM/PM ambiguity — that is the whole point of the 24-hour clock

Switch the direction and type 9:45 PM instead: the headline is 2145, the middle line reads "9:45 PM = 21:45 in 24-hour time", and the spoken line is identical to the one above. The two directions are genuine inverses — nothing is lost or invented in either crossing.

12:15 AM and 12:15 PM: the Pair That Catches Everyone

A quarter past midnight and a quarter past noon are twelve hours apart, and in 12-hour notation the only thing separating them is two letters. In military notation they are 0015 and 1215, which cannot be mistaken for each other at any distance.

Look at the second row: 12:15 PM converts to 1215, the same four digits it already contained. Only three hours of the day behave that way — 10 AM, 11 AM and the noon hour, where 10:45 AM is 1045 and 11:45 AM is 1145 — which is why a botched conversion inside the noon hour can pass unnoticed while the same mistake at midnight cannot.

2400: What Happens When You Type It

The time box accepts 2400 rather than rejecting it, and then normalizes it. The headline comes back as 12:00 AM and the written-out line reads "0000 = 12:00 AM" — the 24 has already become a 00 by the time the answer is printed.

Calculator output — Military → Standard, 2400

12:00 AM · 0000 = 12:00 AM · Spoken: “zero hundred hours” · 0000 is midnight — the day's first minute

Only 2400 exactly is allowed through. Type 2401 or 2430 and you get the guard message "Hours 0–23 (or 2400), minutes 0–59" instead of an answer, because there is no 24th hour to hold minutes in.

930, 0930 and 09:30: Three Ways to Type One Time

In the military-to-standard direction the box is forgiving about shape but strict about digits. A bare 930 is read as 0930, a colon is optional, and even 007 is accepted and read as 0007, which converts to 12:07 AM.

Calculator output — Military → Standard, 930

9:30 AM · 0930 = 9:30 AM · Spoken: “0930 hours” · No AM/PM ambiguity — that is the whole point of the 24-hour clock

What it will not take is a time with no minutes. Typing 17 on its own returns "Enter a 24-hour time like 1730 or 17:30", because the minute pair is not optional — the parser needs two final digits before it will read anything as an hour. Type 1700 or 17:00 instead.

The other direction is strict in a different place. Minutes are optional there — 6 PM and 6PM both convert to 1800, so the space can go as well — but a colon is required the moment you supply minutes: 5:30 PM converts, while 530 PM comes back as "Enter a 12-hour time with AM/PM (e.g., 5:30 PM)". The AM or PM is compulsory too, so a bare 5:30 is refused.

How to Read Your Result

The panel returns four pieces of text every time it succeeds. The first is the answer; the three under it exist so that you can check the answer without trusting it.

The Four Lines

• The headline — the converted time. Converting to standard it carries a suffix, as in 5:30 PM. Converting to military it is four bare digits, as in 1730, with no colon.
• The conversion written out. Going to standard this reads "1730 = 5:30 PM". Going to military it reads "5:30 PM = 17:30 in 24-hour time", with the colon restored and your own typing echoed back in capitals.
• A spoken form, prefixed with "Spoken:" and wrapped in quotation marks.
• A closing note. Three versions exist in the military-to-standard direction: "0000 is midnight — the day's first minute" for the midnight hour, "1200 is noon — no AM/PM ambiguity in 24-hour time" for the noon hour, and "No AM/PM ambiguity — that is the whole point of the 24-hour clock" for the other twenty-two.

In the standard-to-military direction the fourth line is fixed and never varies: "Midnight is 0000 (start of day); 2400 marks the same instant as the END of the previous day". That is the sentence to reach for when a schedule has to say which day a midnight belongs to.

The Spoken Line, and the Two Conventions Behind It

The Spoken line follows three rules and one exception, and it is worth knowing which one produced what you are looking at. A whole hour from 0100 through 0900 is spelled out: 0600 gives “zero six hundred hours”, 0900 gives “zero nine hundred hours”. Midnight is the exception the rule does not reach — 0000 gives “zero hundred hours”, with a single zero rather than the doubled one the pattern would predict. A whole hour of 10 or above keeps its digits: 1300 gives “13 hundred hours”, 2200 gives “22 hundred hours”. And any time with minutes attached is printed as its four digits followed by the word hours, so 1730 gives “1730 hours” rather than a phonetic spelling.

Out in the world there are two different conventions, and they disagree. US military speech reads whole hours as hundreds and appends "hours" — the pattern the line above imitates. Air traffic radio does something else entirely: the FAA's manual gives 0000 as "zero zero zero zero" and 0920 as "zero niner two zero", reading each figure separately, with nine always spoken as "niner" from the same phonetic table that gives "fife" for five.

So treat that line as a reading aid rather than a script. Which version is correct depends on who is listening, and the arithmetic — the part this page is actually for — is identical either way.

What the Time Box Accepts

The Direction control decides which parser runs, and the two parsers want different things. Getting a guard message almost always means the time you typed was valid for the other direction.

• Military → Standard accepts: 1730, 17:30, 0930, 09:30, a bare 930 read as 0930, 007 read as 0007, and 2400 read as 0000.
• Military → Standard refuses: 17 (no minutes), 5:30 PM (wrong direction), 2401 and 2500 (no such hour), 1275 (no such minute).

• Standard → Military accepts: 5:30 PM, 5:30 pm, 5:30 p.m., 6 PM, 6PM, 9 am — the space is optional and the case does not matter.
• Standard → Military refuses: 5:30 and 1730 (no AM or PM), 13:00 PM and 0:30 AM (an hour outside 1 to 12), 5:65 PM (no such minute).

One quirk is worth knowing: a single-digit minute is taken literally rather than padded. Type 5:3 PM and you get 1703, not 1730. Type both minute digits and the ambiguity disappears.

When It Says Check Your Inputs

Four guard messages exist, and each one names its own fix. They appear in place of an answer, in the amber notice rather than the readout.

• "Enter a 24-hour time like 1730 or 17:30" — the military-to-standard parser could not find four digits. Blank boxes, letters and 5:30 PM all land here.
• "Hours 0–23 (or 2400), minutes 0–59" — four digits were found but they are not a real time, as with 2500 or 1275.
• "Enter a 12-hour time with AM/PM (e.g., 5:30 PM)" — the standard-to-military parser found no AM or PM. Typing 1730 in this direction produces it.
• "Hours 1–12, minutes 0–59" — an AM/PM time whose hour is outside 1 to 12, or whose minutes exceed 59.

A direction mismatch accounts for two of the four: 1730 typed while Standard → Military is selected returns the AM/PM message, and 5:30 PM typed in the opposite direction returns the four-digit one. Switching the Direction control fixes both.

When the Converter Runs

The page arrives with 1730 already in the time box and its answer already on screen. That happens because both controls hold a value at load, so the tool runs once at that point. After that it recalculates when you submit the form, not as you type — changing the time and looking at the panel without submitting shows you the previous answer. Reset clears the panel back to its empty state.

The conversion itself is arithmetic done in your browser rather than on a server. The page around it is an ordinary web page and loads analytics and advertising scripts like the rest of this site, so treat it as public rather than private.

Limits: What This Converter Does Not Do

The conversion is exact, because relabeling cannot lose anything. What the four digits do not carry is everything around them — and that missing context is where real scheduling mistakes come from, not from the arithmetic.

No Date, and No Time Zone

A time of day says nothing about which day. 2359 on Friday and 2359 on Saturday are the same four digits, and this box has no field to tell them apart. Neither does it carry a zone: 1730 in one place is a different instant from 1730 in another, and no amount of converting between notations will reconcile the two.

Aviation solves this by fixing the zone rather than the notation. Because the FAA uses UTC for all operations and permits "Zulu" as its spoken name, a time written 1730Z means one instant everywhere on earth. A bare 1730 does not, and that trailing Z is exactly what this converter has no way to attach.

For questions about days rather than the hours inside one — how many days lie between two dates, or what date falls a given number of days out — the tool is the Date Calculator.

Two Local Times Misbehave Twice a Year

Daylight saving breaks the assumption that every four-digit time happens exactly once a day. NIST records the US rule: the change begins on the second Sunday in March, when clocks "must be moved ahead one hour when DST goes into effect so at 2 a.m. it becomes 3 a.m.", and standard time returns on the first Sunday in November at 2 a.m. local time.

The consequence is arithmetic this page cannot fix. On the March date, local times from 0200 to 0259 never occur — a shift booked for 0230 has no start. On the November date, 0100 to 0159 occurs twice, so a 0130 event is genuinely ambiguous until someone says which pass they meant. Converting 0130 to 1:30 AM is still correct, and still does not tell you which 1:30 AM it was.

This is the practical reason logs, flight plans and international schedules are kept in UTC, which has no such discontinuities, and translated to local time only for display.

0000 and 2400 Are One Instant With Two Labels

Both forms mark the same moment; what they disagree about is which date owns it. NIST describes the convention directly, using "0000 to refer to midnight at the beginning of a given day (or date) and 2400 to designate the end of a given day (or date)". A shift ending 2400 Friday and one ending 0000 Saturday finish at the identical second — but a payroll system, a contract or a hospital roster will care very much which of the two is written down.

Because this converter reads a time without a date, it has no basis for preserving that distinction and returns the 0000 form for both. Its own closing line in the standard-to-military direction states the rule, so the information is on screen even though the choice is not yours to make here.

No Seconds, No Suffix, No Subtraction

Minutes are the finest unit available. There is no seconds field, so 1730:45 has nowhere to go, and no way to append a zone letter or a UTC offset to an answer. Real practice does go finer when it has to — the FAA's manual has the current time at a station "stated in the nearest quarter minute" so that pilots can set their clocks against it — but that precision lives outside a four-digit time.

The larger limit is that this is a converter, not a clock arithmetic tool. It translates one time; it will not subtract 0800 from 1630, add forty minutes to 2340 and roll past midnight, or total a week of shifts. Those are different operations, and doing them by hand in 24-hour notation is easy to get wrong because the hour column carries at 60 rather than at 100.

That last trap has its own fix: 1630 minus 0800 is 8 hours 30 minutes, which payroll wants as 8.5 rather than 8.30, and the conversion between the two is the Hours to Decimal Calculator.