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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:
| |
Standard time |
Daylight saving time |
| Eastern |
Add 5 Hours |
Add 4 Hours |
| Central |
Add 6 Hours |
Add 5 Hours |
| Mountain |
Add 7 Hours |
Add 6 Hours |
| Pacific |
Add 8 Hours |
Add 7 Hours |
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:
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To obtain Military time from local time:
After 12 PM, add or subtract 12
Before 12 PM, do nothing
Example:
2:00 pm: 2 + 12 = 14 or 1400 Military time
10:00 am = 1000 (ten hundred hours)
8:00 am = 0800 (zero eight hundred hours)
To obtain local time when Zulu time is known:
Zulu Time – Factor = Local Military time
To obtain Zulu time when local time is known:
Local Military Time + Factor = Zulu Time
Factor is the offset from GMT (Greenwich
Mean Time). It can be obtained
from the Airport / Facility Directory (A/FD)
|
|
Local Time |
Local Military Time |
Zulu Time (Summer +5) |
Zulu
Time (Normal +6) |
| 12:00 AM |
0000 |
0500 |
0600 |
| 1:00 AM |
0100 |
0600 |
0700 |
| 2:00 AM |
0200 |
0700 |
0800 |
| 3:00 AM |
0300 |
0800 |
0900 |
| 4:00 AM |
0400 |
0900 |
1000 |
| 5:00 AM |
0500 |
1000 |
1100 |
| 6:00 AM |
0600 |
1100 |
1200 |
| 7:00 AM |
0700 |
1200 |
1300 |
| 8:00 AM |
0800 |
1300 |
1400 |
| 9:00 AM |
0900 |
1400 |
1500 |
| 10:00 AM |
1000 |
1500 |
1600 |
| 11:00 AM |
1100 |
1600 |
1700 |
| 12:00 PM |
1200 |
1700 |
1800 |
| 1:00 PM |
1300 |
1800 |
1900 |
| 2:00 PM |
1400 |
1900 |
2000 |
| 3:00 PM |
1500 |
2000 |
2100 |
| 4:00 PM |
1600 |
2100 |
2200 |
| 5:00 PM |
1700 |
2200 |
2300 |
| 6:00 PM |
1800 |
2300 |
0000 |
| 7:00 PM |
1900 |
0000 |
0100 |
| 8:00 PM |
2000 |
0100 |
0200 |
| 9:00 PM |
2100 |
0200 |
0300 |
| 10:00 PM |
2200 |
0300 |
0400 |
| 11:00 PM |
2300 |
0400 |
0500 |
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For example, the Texas A/FD shows that the
offset for Houston is -6(-5DT). This means that this time zone is
6 hours behind Greenwich, and when daylight saving time is active, it is
5 hours behind.
Examples:
Determine Zulu time for a local time of
3:45 PM, and time zone of Central Standard Time (CST) (UTC-6(-5DT))
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 + 6 Hours = 2145Z
Determine Zulu time for a local time of
9:30 AM, and time zone of Central Daylight Time (CDT) (UTC-6(-5DT))
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 + 5 hours = 3:30 PM
(Note we used 5, and not 6. In
this example, we are on daylight saving time. (CDT))
3pm is after 12pm, so we add 12 (3 + 12 =
15), so 3:30 PM = 1530 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:
www.naco.faa.gov/index.asp?xml=naco/online/d_afd
For more information, follow the link below to the FAA's AIM
(Aeronautical Information Manual) article on Time:
www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/aim/Chap4/aim0402.html#4-2-12
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