Zulu Time

Zulu Time – What is it and why is it important?

With all the time zones in the world, pilots need a way to reference the current, past or future time, and not have to worry about what time zone they are in.

This is where Zulu Time comes into play. Because a pilot may cross several time zones during a flight, a standard time system has been adopted. It is called Universal Coordinated Time (UTC) and is referred to as Zulu time. UTC is the time at the 0 line of longitude which passes through Greenwich, England. All of the time zones around the world are based on this reference. It is presented in the local Military time at Greenwich, England.

To convert to this time in the United States, a pilot should do the following:

For daylight saving time, 1 hour should be subtracted from the calculated times. Taken from the Pilots handbook of aeronautical knowledge FAA-8083-25

In order to determine Zulu time, you must first convert the local time into military time:

For example, the Ohio A/FD shows that the offset for Cleveland is -5(-4DT). This means that this time zone is 5 hours behind Greenwich, and when daylight saving time is active, it is 4 hours behind.

Examples:

Determine Zulu time for a local time of 3:45 PM, and time zone of Eastern Standard Time (EST) (UTC-5(-4DT))
3pm is after 12pm, so we add 12 (3 + 12 = 15), so 3:45 PM = 1545 Military
To obtain Zulu time when local time is known: Local Military Time + Factor = Zulu Time
1545 + 5 Hours = 2045Z

Determine Zulu time for a local time of 9:30 AM, and time zone of Eastern Daylight Time (EDT) (UTC-5(-4DT))
9 AM is before 12 pm, so we don’t add or subtract anything to get military time: 9:30 AM = 0930 Local Military Time
To obtain Zulu time when local time is known: Local Military Time + Factor = Zulu Time
0930 + 4 hours = 1:30 PM
(Note we used 4, and not 5. In this example, we are on daylight saving time. (EDT))
3pm is after 12pm, so we add 12 (3 + 12 = 15), so 3:30 PM = 1530 Military Time
1530 + 4 = 1930 Zulu Time

Determine local time for a Zulu time of 1710Z, and time Zone of Eastern Daylight Time (EDT) (UTC-5(-4DT))
To obtain local time when Zulu time is known: Zulu Time  Factor = Local Military time
1710 – 4 hours = 1310 Local Military time
(Note we used 4, and not 5. In this example, we are on daylight saving time. (EDT))
13 is greater than 12, so our time will be in PM. We subtract 12, and get 1
1310 Local Military time = 1:10 PM

NACO has made the A/FD digitally available to the public. You can download and print excerpts from any A/FD in print from the internet: A/FD

For more information, follow the link below to the FAA’s AIM (Aeronautical Information Manual) article on Time: Aeronautical Information Manual