Date & time · Date-time group
Date-time group (DTG) tool.
Build a DTG such as 201430ZOCT26 from a date and time zone letter, or paste one to see the local and Zulu time it stands for. Runs in your browser.
Format or decode
Result
Build a DTG from a date, or decode one you have.
What is a DTG?
A date-time group (DTG) is a compact string that packs the day, time, time zone, and usually the month and year into one token, so a message or log entry can be dated unambiguously. The US military layout, as described by Wikipedia, is DD HHMM (SS) Z MON YY with optional spaces: two-digit day, two-digit hour and minute, optional seconds, the time zone letter, a three-letter month and a two-digit year. Esri's ArcGIS help gives the same pattern, ddHHmm'Z' MMM yy, with 121145ZJAN11 as an example.
The three forms
| Form | Layout | Example | Stated use |
|---|---|---|---|
| Full | DDHHMMSSZMONYY | 20005349ZOct26 | Software timestamps |
| Standard | DDHHMMZMONYY | 091630Tjul11 | Manually written timestamps |
| Short | DDHHMMZ | 051100Z | Planning |
The three examples are the ones Wikipedia gives. 20005349ZOct26 is 20 October 2026, 00:53:49 UTC. 091630Tjul11 is 9 July 2011, 16:30 in zone T (UTC-7), which is 23:30 Zulu. 051100Z is the 5th of the current month at 11:00 Zulu; because it names no month or year, you need context, which is why the decoder asks for a reference month.
Reading a DTG field by field
Take the hypothetical 201430ROCT26. 20 is the day, 14 the hour, 30 the minute, R the zone (Romeo, UTC-5), OCT the month and 26 the year. The clock reading is 14:30 on 20 October 2026 in zone R, which is 19:30 Zulu the same day. If the group were 201930ZOCT26, the same moment, the zone letter would be Z instead. Both are valid; the letter simply says which clock the digits belong to. Writing Z after local digits is the classic mistake, because it silently shifts the moment by the zone's offset.
Edge cases and mistakes
The day number does not exist in every month: 311200ZNOV26 is rejected because November has 30 days. Hours run 00 to 23 and minutes 00 to 59. A two-digit year is read here as 20YY, an assumption of this tool, so 99 means 2099, not 1999. J means the writer's local time and has no UTC offset, so a J group cannot be converted to Zulu. Wikipedia notes a DTG can serve as a message identifier only if it is unique for each message, which a clock reading alone does not guarantee. The Wikipedia text states the zone is included when it differs from UTC but also shows the US military pattern as always carrying a letter; this tool always writes the letter.
Who this is for
Staff officers and cadets learning message format, GIS analysts converting DTG text fields (the ArcGIS example above), writers who want a believable timestamp, and anyone who has seen "what is DTG" in a document header.
What this does not cover
It does not validate message formats beyond the date-time group, does not know any unit's publication rules, and does not guess a year before 2000. For internet timestamps use the RFC 3339 validator; for a plain Zulu conversion use the Zulu time converter.
FAQ
What is a DTG?
A date-time group is a compact code for day, time, time zone, month and year, for example 201430ZOCT26. It dates a message or log entry in one token.
How do you read 201430Z?
Day 20, 14:30, in zone Z (Zulu, UTC). With a month and year added, as in 201430ZOCT26, it is 20 October 2026 at 14:30 UTC.
What format is a military DTG?
DD HHMM (SS) Z MON YY, with optional spaces: day, hour, minute, optional seconds, zone letter, three-letter month and two-digit year. Short forms drop the month and year.
Is a DTG always in Zulu time?
No. The letter says which zone the clock digits are in. Z means Zulu (UTC). R, for example, means the digits are Eastern Standard Time, UTC-5.
How do I write a DTG for local time?
Use the letter of your zone. J exists for local time but has no fixed offset, so a J group cannot be converted to Zulu. This tool formats any lettered zone and shows the Zulu equivalent.
Does a DTG include seconds?
Only the full form does: DDHHMMSSZMONYY, listed by Wikipedia for software timestamps. The standard and short forms stop at minutes.
How do I convert DTG text to a date field in ArcGIS?
Esri documents the custom date-time pattern ddHHmm'Z' MMM yy for strings like 121145Z JAN 11, and ddHHmm'Z'MMMyy when there are no spaces. Set the output format to DATE.
Why does the decoder ask for a reference month?
A short DTG such as 051100Z has no month or year. Without one the tool cannot check the day exists or give a calendar date, so you pick the month it belongs to.
Sources (each opened 2026-10-20): Wikipedia, Date-time group (cites MIL-STD-2500A and Federal Standard 1037C); Esri ArcGIS 10.2 help, Converting Date-Time Group (DTG) formatted text into Date-Time geodatabase fields; Wikipedia, List of military time zones (cites ACP 121(I), CCEB, October 2010). MIL-STD-2500A and ACP 121, which Wikipedia cites for the format, were not fetched; the format here follows Wikipedia and the Esri documentation.