EST is 5 hours behind Zulu, and EDT is 4 hours behind Zulu. Live clocks, the full hour chart and the daylight saving rule that catches people out.
Zulu time is UTC - the clock every flight plan, order and server log is written in, precisely because it never moves. Eastern Standard Time (EST) sits UTC−5, which makes it 5 hours behind Zulu. In everyday speech the zone is just "Eastern time". Converting one to the other is a single addition, and the only two things that go wrong are the date and daylight saving.
The converter above tracks the current time until you type into it. Enter any Zulu time - 1730Z, 17:30Z or NOW - and it renders the same instant in EST in 24-hour, 12-hour and dated form. The chart below is the same conversion for every hour of the day, so it can be read without typing anything at all.
Every hour from 0000Z to 2300Z. Two columns, because the zone has two offsets: read the EST column in winter and the EDT column from the second Sunday in March to the first Sunday in November. A single column here would be wrong for most of the year. Where the sum crosses midnight the date moves with it, marked in the cell.
| Zulu | ESTUTC−5 | EDTUTC−4 |
|---|---|---|
| 0000Z | 19:00 −1 day | 20:00 −1 day |
| 0100Z | 20:00 −1 day | 21:00 −1 day |
| 0200Z | 21:00 −1 day | 22:00 −1 day |
| 0300Z | 22:00 −1 day | 23:00 −1 day |
| 0400Z | 23:00 −1 day | 00:00 |
| 0500Z | 00:00 | 01:00 |
| 0600Z | 01:00 | 02:00 |
| 0700Z | 02:00 | 03:00 |
| 0800Z | 03:00 | 04:00 |
| 0900Z | 04:00 | 05:00 |
| 1000Z | 05:00 | 06:00 |
| 1100Z | 06:00 | 07:00 |
| 1200Z | 07:00 | 08:00 |
| 1300Z | 08:00 | 09:00 |
| 1400Z | 09:00 | 10:00 |
| 1500Z | 10:00 | 11:00 |
| 1600Z | 11:00 | 12:00 |
| 1700Z | 12:00 | 13:00 |
| 1800Z | 13:00 | 14:00 |
| 1900Z | 14:00 | 15:00 |
| 2000Z | 15:00 | 16:00 |
| 2100Z | 16:00 | 17:00 |
| 2200Z | 17:00 | 18:00 |
| 2300Z | 18:00 | 19:00 |
The conversions people reach this page for, answered in one line each. The first time is EST; the EDT time next to it applies from the second Sunday in March to the first Sunday in November.
Take the four digits, subtract 5 hours, and roll the date if the result falls outside 00:00-23:59. 1730Z becomes 12:30 EST; 0200Z becomes 21:00 EST the previous day.
Between the second Sunday in March to the first Sunday in November the zone is on Eastern Daylight Time, so the correction becomes subtract 4 hours instead. Same instant, different local label - 1730Z is 13:30 EDT.
Controllers and forecasters often drop the minutes and write a bare hour: 16Z means 1600Z, 6Z means 0600Z. Pad it back to four digits and the chart above answers it directly.
Do the arithmetic in Zulu and convert once, at the end, for whoever needs a local time. Adding en-route time to a departure slot in local time and converting afterwards is how the day boundary gets lost. The Zulu time converter does both halves in one box.
Going the other way is the same arithmetic reversed: take the EST time, add 5 hours, and write the result as four digits with a Z suffix. 07:00 EST is 1200Z. If the sum crosses midnight the date moves too, exactly as in the chart, just in the other direction.
When the clock on the wall reads EDT, the correction is add 4 hours instead: 08:00 EDT is also 1200Z. Same instant, one hour less to undo.
EST and EDT are different offsets and both get called "Eastern time" in conversation. For roughly eight months of the year the US East Coast is on EDT, four hours behind Zulu, not five - so a briefing converted with the EST column in July lands an hour early.
Zulu itself never shifts, so every hour of the shift lands on the local side of the conversion: UTC−5 in winter, UTC−4 from the second Sunday in March to the first Sunday in November. If a message does not say which, use the date it was written on to decide, and read the matching column above.
The Eastern zone covers Washington, New York, Atlanta and Miami, which puts most US federal, financial and East Coast military traffic on it. Flight plans out of KJFK, KDCA and KATL are filed in Zulu and read back in local Eastern.
Flight plans, METARs, TAFs, NOTAMs and ATC clearances are all in Zulu, and so are military orders, satellite passes and incident timelines. The conversion to EST is the last step, for the people who have to be somewhere at a local hour - a briefing time, a crew report, a maintenance window. Written the aviation way it carries the day of the month too: 141730Z is the 17:30 Zulu of the 14th, which removes the last ambiguity a date shift can create. See military time for the four-digit notation itself.
The same Z closes every ISO 8601 timestamp: a log line stamped 2026-08-20T16:37:05Z happened at 1637Z, and it converts to EST with the same arithmetic as any briefing time.
EST is 5 hours behind Zulu (UTC−5). To convert, take the Zulu time and subtract 5 hours: 1200Z is 07:00 EST. During Eastern Daylight Time it is 08:00 EDT instead.
The abbreviation EST always means UTC−5, but the clock it describes switches to EDT (UTC−4) from the second Sunday in March to the first Sunday in November. Zulu never changes, so the gap between them is an hour smaller during EDT.
0000Z is 19:00 EST the previous day. The date rolls back, which is the shift people most often lose. On daylight time it is 20:00 EDT the previous day.
Yes, for every practical purpose. Zulu is how UTC is written and spoken in aviation and military use - the Z suffix is the phonetic letter for the zero-offset zone. GMT is the older name for the same clock reading, though the UK itself moves to BST in summer.
Reverse the arithmetic: add 5 hours and add the Z suffix. Do the maths in Zulu first and convert once at the end - converting first and adding afterwards is where the date boundary gets lost.
Printed from tcalc.it - free Zulu time converters, hour charts and the daylight saving rules.