CET is 1 hour ahead of Zulu, and CEST is 2 hours ahead of 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. Central European Time (CET) sits UTC+1, which makes it 1 hour ahead of Zulu. 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 CET 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 CET column in winter and the CEST column from the last Sunday in March to the last Sunday in October. 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 | CETUTC+1 | CESTUTC+2 |
|---|---|---|
| 0000Z | 01:00 | 02:00 |
| 0100Z | 02:00 | 03:00 |
| 0200Z | 03:00 | 04:00 |
| 0300Z | 04:00 | 05:00 |
| 0400Z | 05:00 | 06:00 |
| 0500Z | 06:00 | 07:00 |
| 0600Z | 07:00 | 08:00 |
| 0700Z | 08:00 | 09:00 |
| 0800Z | 09:00 | 10:00 |
| 0900Z | 10:00 | 11:00 |
| 1000Z | 11:00 | 12:00 |
| 1100Z | 12:00 | 13:00 |
| 1200Z | 13:00 | 14:00 |
| 1300Z | 14:00 | 15:00 |
| 1400Z | 15:00 | 16:00 |
| 1500Z | 16:00 | 17:00 |
| 1600Z | 17:00 | 18:00 |
| 1700Z | 18:00 | 19:00 |
| 1800Z | 19:00 | 20:00 |
| 1900Z | 20:00 | 21:00 |
| 2000Z | 21:00 | 22:00 |
| 2100Z | 22:00 | 23:00 |
| 2200Z | 23:00 | 00:00 +1 day |
| 2300Z | 00:00 +1 day | 01:00 +1 day |
Take the four digits, add 1 hour, and roll the date if the result falls outside 00:00–23:59. 1730Z becomes 18:30 CET; 0200Z becomes 03:00 CET.
Between the last Sunday in March to the last Sunday in October the zone is on Central European Summer Time, so the correction becomes add 2 hours instead. Same instant, different local label — 1730Z is 19:30 CEST.
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.
Continental Europe is on CEST, two hours ahead of Zulu, for seven months of the year. The EU switches on the last Sunday of March and October, two weeks off the US dates, so for two windows each year the Europe-to-US gap is an hour different from usual.
Zulu itself never shifts, so every hour of the shift lands on the local side of the conversion: UTC+1 in winter, UTC+2 from the last Sunday in March to the last Sunday in October. If a message does not say which, use the date it was written on to decide, and read the matching column above.
Paris, Berlin, Rome, Madrid, Warsaw and Prague. NATO and EUROCONTROL traffic is coordinated in Zulu precisely because the civil clock underneath it moves twice a year.
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 CET 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.
CET is 1 hour ahead of Zulu (UTC+1). To convert, take the Zulu time and add 1 hour: 1200Z is 13:00 CET. During Central European Summer Time it is 14:00 CEST instead.
The abbreviation CET always means UTC+1, but the clock it describes switches to CEST (UTC+2) from the last Sunday in March to the last Sunday in October. Zulu never changes, so the gap between them is an hour smaller during CEST.
0000Z is 01:00 CET. On daylight time it is 02:00 CEST.
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: subtract 1 hour 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.