10 PM to Military Time

10 PM is 2200: one addition and a pair of zeros

The conversion needs one move. The hour is 10 and the time falls in the evening, so the hour gains 12: 10 + 12 = 22. The time falls exactly on the hour, so the minute digits are 00. Put the two pairs together and the answer is 2200, the same reading a 24-hour clock shows as 22:00.

The zeros carry the minute field. A 24-hour reading always holds four digits, an hour pair then a minute pair, and both digits of the minute pair stay even when the minutes are zero. Drop them and you get a three digit reading that belongs to a different time: 220 padded to four digits is 0220, which is 20 past 2 in the morning.

Why 12 and not some other number? The 24-hour clock counts straight from 0 at midnight to 23 at 11 PM, so every evening hour equals its 12-hour number plus 12. The 10 at night is the 22nd hour of the day, sitting 12 hours after the morning 10.

The whole-hour ladder from noon to midnight

Read the 10 PM row against its morning twin. 10 AM is 1000 and 10 PM is 2200, and the two readings sit 12 hours apart, which is 720 minutes. In the 12-hour system the AM and PM tags do the separating; in the 24-hour system the number itself does it. That is why schedules, logs and machine timestamps prefer the 24-hour form: no two readings on the dial can be confused with each other.

2200 on a timesheet

Decimal hours divide the minutes by 60 and add them to the hour. At 2200 the minutes are 00, so the decimal value is 22.00 with nothing left over, and the minutes elapsed since midnight run 22 x 60 = 1,320. A timesheet that logs a 2200 start and a 0600 end records 8 hours 00 minutes, or 8.00 decimal hours.

The pay math follows the decimals. At $21.40 an hour, an 8.00 hour shift starting at 2200 earns 8 x 21.40 = $171.20. At $18.75 the same shift earns $150.00. The converter above runs the arithmetic at whatever rate you enter and keeps the result to two decimal places, which is what most payroll systems expect.

Two hours remain in the day after 2200. Midnight arrives 2 hours later, 120 minutes, and the readings 2400 on one date and 0000 on the next name the same instant. The Times of Day FAQs from NIST draws the line the same way: 0000 refers to midnight at the start of a date and 2400 to the end of one.

Saying and writing 2200

Whole hours are spoken with the word hundred: 2200 is twenty-two hundred, or twenty-two hundred hours on a formal log. Radio procedure reads every digit on its own, so the same time becomes two two zero zero, a style that survives noise better than the compressed form. The moment minutes appear the speech changes shape: 2205 is twenty-two oh five and 2245 is twenty-two forty-five.

In writing, the four digit form without a colon is the military and log convention, while 22:00 with a colon is the international form carried by ISO 8601 and most of the world's digital clocks. Both mean ten at night. A 12-hour rendering, 10:00 p.m., describes the same instant with the period carried by the tag instead of the number.

What a 2200 start means in practice

A 2200 start marks the late part of the day. Businesses that close at 2200 spend their final 2 hours winding down, and a handwritten 10 PM sits one careless stroke away from 10 AM, which is why posted schedules that matter tend to use the four digit form.

Shift work is where the reading earns its keep. A shift posted as 2200 to 0600 spans midnight, and the 24-hour form makes the span unambiguous: 2200 comes before 0600 of the next date. Written as 10 PM to 6 AM, the same posting invites the question of which day each time belongs to, and on a rota that question affects pay, rest rules and handover.

The reading also travels poorly across the map. Local 2200 is 2200 in one time zone at a time, which the next section takes up. Timetables and logs that cross zones either name the zone outright or write the time in Zulu, the 24-hour UTC reading.

2200 is a clock reading, not a time zone

2200 says where you are in the day, not where you are on the map. Add the zone and the same four digits land on different UTC readings. In winter, Eastern Standard Time runs 5 hours behind UTC, so 2200 EST is 0300Z the next day: 22 + 5 = 27, and 27 - 24 = 3. In summer, Eastern Daylight Time runs 4 hours behind, so 2200 EDT is 0200Z the next day.

The Z suffix marks UTC. The Universal Time page from the U.S. Naval Observatory notes that times in UT are almost always written on a 24-hour clock, sometimes with a Z appended as in 0935Z. Read the other way, 2200Z is 1700 in Eastern Standard Time (22 - 5 = 17) and 1400 in Pacific Standard Time (22 - 8 = 14).

Daylight saving moves the local reading by an hour twice a year without touching UTC at all, so a log kept in Z needs no seasonal correction while one kept in local time does. That asymmetry is the main reason time sensitive operations keep their records in Z.

Reading 2200 back to 10 PM

The reverse move subtracts 12 from any hour 13 through 23. For 2200: 22 - 12 = 10, and the hour sits past noon, so the tag is PM and the reading is 10 PM. Minutes copy across untouched, so 2245 is 10:45 PM and 2215 is 10:15 PM.

The hours 00 through 11 never subtract anything: 0900 is 9 AM and 0000 is midnight. The rule splits at 12 and 13, and 1200 is the hinge that keeps its number in both directions. A quick sanity check on any reading: a valid 24-hour time falls between 0000 and 2359, so 2400 describes the end of a date rather than a moment inside it.

Where a 10 PM conversion goes wrong

The most common error is direction. 1000 is 10 in the morning and 2200 is 10 at night, and the two sit 12 hours apart. Writing 1000 for an evening event schedules it at breakfast time, and on systems that sort by timestamp the mistake stays invisible until someone checks the log.

The second is the minute pair. 2200 needs both digits of the minute field, and 220 is not an accepted short form: a three digit reading pads on the left to 0220, which is 20 past 2 in the morning. The third is noon and midnight. 12 PM is 1200 with no addition and 12 AM is 0000, and the ambiguity that NIST flags in the 12-hour form is the reason the 24-hour form exists at all.

The fourth shows up at the end of the day. Most systems close a date at 2359, while some logs write 2400 for the closing boundary, and 0000 belongs to the opening date while 2400 belongs to the closing one. When you need to know what the official time is right now, the official U.S. time from time.gov gives the authoritative reading, and the converter above handles any hour you feed it, morning or evening.