What Zulu time is
Zulu time is another name for Coordinated Universal Time (UTC): the time at the 0° line of longitude through Greenwich, England, on which every time zone in the world is based. "Because a pilot may cross several time zones during a flight," the FAA's Pilot's Handbook explains, aviation uses this one standard instead of local time. The FAA uses UTC for all its operations, and on the radio "the term 'Zulu' may be used to denote UTC" (Aeronautical Information Manual 4-2-12). Zulu is simply how the phonetic alphabet says Z, the letter written after a UTC time.
Times are written on the 24-hour clock as four figures: 9 a.m. is 0900, 1 p.m. is 1300 and 10 p.m. is 2200. On the radio they are read figure by figure: 0920 is "zero niner two zero".
Converting Zulu time to local time
The Aeronautical Information Manual gives the conversion for standard time, and the same table appears in the Pilot's Handbook:
| Time zone | Standard time to Zulu | Daylight time to Zulu |
|---|---|---|
| Eastern | Add 5 hours (EST, UTC−5) | Add 4 hours (EDT, UTC−4) |
| Central | Add 6 hours (CST, UTC−6) | Add 5 hours (CDT, UTC−5) |
| Mountain | Add 7 hours (MST, UTC−7) | Add 6 hours (MDT, UTC−6) |
| Pacific | Add 8 hours (PST, UTC−8) | Add 7 hours (PDT, UTC−7) |
| Alaska | Add 9 hours (AKST, UTC−9) | Add 8 hours (AKDT, UTC−8) |
| Hawaii | Add 10 hours (HST, UTC−10) | No daylight time |
"For daylight time, subtract 1 hour," as the manual puts it. Going from Zulu to local time, subtract the hours instead. The manual's own example reads 0920 UTC as 0120 Pacific, one twenty a.m.: Pacific standard time is UTC−8.
Watch the date. Every US zone is behind Zulu, so on a US evening Zulu has already reached tomorrow: 0230Z on October 2 is 22:30 EDT, 10:30 p.m., on October 1. The converter shows both dates, and the chart shades the hours that fall on the day before.
Times in METARs, TAFs and NOTAMs
- METAR and SPECI: the six-figure group after the station, such as
161753Z, is the day of the month and the time of the observation, always in UTC. - TAF:
081125Zis when the forecast was issued, and0812/0912is the valid period, from the 8th at 1200Z to the 9th at 1200Z. A period that ends at midnight UTC ends in 24, as in0900/0924. - NOTAM: times are in UTC as ten figures, year, month, day, hour and minute:
2610011600is October 1, 2026, at 1600Z.
Paste any of these groups into the converter and it takes the date from it too; a METAR group's month is taken as the one that puts the day nearest to today. The METAR decoder and TAF decoder show each report's times in plain English.
Daylight saving time
US daylight saving time starts at 2 a.m. local time on the second Sunday in March and ends at 2 a.m. on the first Sunday in November (15 U.S.C. 260a). Zulu time does not change; local time does, so the difference shrinks by an hour in summer.
Not everyone moves their clocks. Daylight saving time is not observed in Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands or Arizona, except on the Navajo Nation, which does observe it (NIST). Arizona's MST, UTC−7, therefore matches Pacific daylight time in summer and Mountain standard time in winter.
Other countries change on other dates: the UK, for example, moves to British Summer Time on the last Sunday in March and back to Greenwich Mean Time on the last Sunday in October (GOV.UK). The converter uses your browser's time zone database for the date you enter, so it applies each zone's own rules. In the US, on the night the clocks go back, local times from 1 to 2 a.m. happen twice, and the converter shows both Zulu times; on the night they go forward, local times from 2 to 3 a.m. do not exist, and it says so.
Sources
- FAA, Aeronautical Information Manual, 4-2-7 (phonetic alphabet) and 4-2-12 (time).
- FAA, Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C): NOTAM times, page 1-14; METAR and TAF date and time groups, pages 13-6 and 13-9; time zones and UTC, page 16-5; glossary, "Zulu time".
- 15 U.S.C. 260a, advancement of time or changeover dates.
- NIST Time and Frequency Division, "Daylight Saving Time (DST)".
- GOV.UK, "When do the clocks change?"
How to convert Zulu time to local time
- Find your time zone's offset from UTC. Eastern standard time is UTC−5; in daylight saving time, Eastern is UTC−4.
- Subtract those hours from the Zulu time: 1753Z is 12:53 EST in winter and 13:53 EDT in summer.
- If the result goes below 00:00, add 24 hours and go back one day: 0230Z on the 2nd is 21:30 EST on the 1st.
- To turn local time into Zulu, add the hours instead: 1:20 a.m. Pacific standard time plus 8 hours is 0920Z.
Questions pilots ask
What is Zulu time?
Zulu time is Coordinated Universal Time (UTC), the time at 0° longitude, which passes through Greenwich, England. Aviation uses it so that a flight plan, weather report or NOTAM means the same moment everywhere: the FAA uses UTC for all operations. Zulu is the phonetic alphabet's word for Z, the letter written after a UTC time.
What time is it in Zulu now?
The clock at the top of this page shows the current Zulu time to the second, with your local time beside it. It runs from this device's clock.
How many hours is Eastern time behind Zulu?
Five hours in standard time (EST, UTC−5) and four in daylight saving time (EDT, UTC−4). Central is six and five hours behind, Mountain seven and six, Pacific eight and seven, Alaska nine and eight, and Hawaii ten all year.
Is Zulu time the same as GMT?
In winter, yes: the UK is on Greenwich Mean Time, which reads the same as Zulu. From the last Sunday in March to the last Sunday in October the UK is on British Summer Time, one hour ahead, so London time is then Zulu plus one hour.
Does Zulu time change for daylight saving time?
No. UTC is the same all year; local clocks move instead. In most of the US the gap to Zulu shrinks by an hour from the second Sunday in March to the first Sunday in November.
What does the Z in 161753Z mean?
That the time is given in Zulu (UTC) rather than local time. In a METAR the first two figures are the day of the month and the last four the time, so 161753Z is the 16th at 17:53 UTC. Type it into the converter and it sets the date as well.