How to use the military date-time group converter
- Choose Write a group to turn a date and time into a group, or Read a group to decode one.
- To write, pick the date, enter the time on a 24-hour clock and choose the zone letter that applies to that time.
- To read, type a group such as 311430Z JAN 26. A year with four digits also works, and the century setting under More options places two-digit years.
- Read the group, the local date and time, the UTC date and time, and the group written in Zulu time.
Formula
group = DD HH MM + zone letter + month (3 letters) + year
UTC = written time - zone offset
zone offsets: Z 0, A to I +1 to +9, K to M +10 to +12, N to Y -1 to -12
The letter J is skipped in the run of letters because it means the reader's local time. Subtracting the offset can move the date, the month and even the year, and the page handles that with whole days.
Two groups
14:30 on 31 January 2026 in zone Z is written 311430Z JAN 26, and its UTC time is the same, 2026-01-31 14:30.
The group 010005Q MAR 24 is 00:05 on 1 March 2024 in zone Q, which is 4 hours west of UTC, so UTC is 04:05 on the same day. A time of 14:30 in zone R (5 hours west) is 19:30 UTC.
Reading a group
The first six digits are the day, hour and minute. The letter after them tells you which time zone those figures are in, and Z (Zulu) is UTC. The month is written with three letters and the year with two digits or four. Because the letters A to M run east and N to Y run west, you can tell the offset at a glance.
To convert plain 24-hour times and print a chart, use the Military Time Converter. For named time zones with daylight saving, use the Time Zone Converter.
Variations
Organizations differ in spacing, the use of the year and extra marks, such as a month and year after a slash. The page accepts the common style, with or without spaces, and writes the standard style with spaces. Check the style guide you are required to follow before using a group in a formal document.
Assumptions and limits
- Dates are in the Gregorian calendar and the day must exist in the month, including 29 February in leap years.
- A two-digit year is placed in the century you set, 2000s by default.
- Zone J has no fixed offset, so no UTC time is shown for it.
- Daylight saving time is not applied; the zone letter you pick is the zone the time is written in.
- Seconds are not part of a group and are ignored.
Frequently asked questions
What does the Z in 311430Z mean?
It marks Zulu time, which is UTC. The phrase comes from the radio alphabet word for Z.
Why is there no zone letter J in the list of offsets?
J is not used for a fixed zone. It means the local time of the person reading the group.
How do I write midnight?
Use 0000 for the start of the day. The page writes 00:00 as 00 hours 00 minutes on the date you chose.
Can a group cross into the next day when converted to UTC?
Yes. 23:30 in zone R is 04:30 UTC the next day, and the page shows the new date and month.