Weather products use coordinated universal time, or Zulu time. This is the time in Greenwich, England, used in aviation as the worldwide time zone, in order to avoid confusion which would arise from constantly dealing with different time zones.

To convert Zulu time to local time, you need only know how many hours ahead or behind your time zone is, compared to Greenwich time. For example, since the eastern time zone is five hours behind Greenwich time, 1200 Zulu time is 7:00 AM eastern time.

If you were in the central time zone, you would subtract six hours…mountain, seven…and pacific, eight. So, 1200 Zulu time is the same as 7:00 AM eastern, 6:00 AM central, 5:00 AM mountain, and 4:00 AM pacific.

Zulu time uses the 24 hour clock, instead of using AM and PM.

With the 24 hour clock, zero hundred to 12 hundred is midnight to noon, representing the AM hours, and 12 hundred to 24 hundred hours is noon to midnight, representing the PM hours.

Conversion can logically be made between the 12 and 24 hour clocks by adding or subtracting 12, as necessary.

If a weather report were issued at 2045Z, that would equal 1545 eastern time, since eastern time is five hours behind Greenwich time.

A time of 1545 eastern on the 24 hour clock is the same as 3:45 PM eastern time.

Conversion to Zulu

To convert local time to Zulu time, simply reverse the math.

For example, 3:45 PM, which is 1545 eastern time, equals 2045 Zulu time, since Greenwich is five hours ahead of eastern time.

Daylight Savings Time

In areas where daylight savings time is observed, a one hour compensation must be made during daylight savings. This means during daylight savings, eastern time is only four hours behind Greenwich, instead of five. Likewise, during daylight savings, central time is 5 hours behind, mountain six, and pacific, seven. So, 1200 Zulu time equals 7:00 AM eastern standard time, and 8:00 AM eastern daylight savings time.