Well, I’ve been cut to the quick. I crowed recently about being able to watch ST:TOS while doing my cardio at the gym, but the channel recently replaced it with Sanford and Son.
So I’ve been watching JAG on USA, the show about Navy legal officers. I’ve noticed that at the beginning of every segment, there will be a little message at the bottom with the location and time. The time is always something like “1430 Zulu”.
I know that Zulu is simply the name for ‘z’ in the word-alphabet they use in the Navy, but why do they need it every time they give the time?
There are 24 time zones, and a letter has been given to each. Z has been given to UTC time, which is the time that used to be called “Greenwich Mean Time” So, 1430 Zulu means that it’s 2:30 PM in London/Paris/that time zone.
It’s military convention. “Zulu” time is the equivalent of Greenwich mean time (or maybe Universal Time, I can never remember if those are the same or not). So by giving a time of “0600 Zulu”, people in different time zones (and different observances of DST) can adjust for their particular location. So a commander in Washington DC (GMT -5) would know that time would be 1 AM for him.
Each time zone has a letter designation. “Alpha” is GMT +1, “Bravo” GMT +2, continuing around the globe to “Mike” at GMT +12 (“J” is skipped). “November” starts at GMT -1. And “Zulu” is GMT +0.
And it seems that my search for a cite left me out of the four-way simulpost.
because military operations are happening all over the world, they will use zulu time as a reference point, individual units will convert it to local time as needed.
It’s used in civilian aviation for the same reasons the military use it. It’s a convenient common time to convert other time zones to when calculating the timing of activities in different time zones. It also sounds cool ;).
Zulu is not quite the same as London time, as Zulu/UTC/GMT does not have daylight saving applied to it. There is some technical difference between UTC and GMT but they can be considered to be the same thing for most of us.
When a time zone is on the half hour, such as Darwin which is UTC+9.5, the two letters on either side of the time zone are combined. Darwin time is referred to as India Kilo with India being UTC+9 and Kilo UTC+10 (remembering that Juliet is omitted from the system.)
Because my work is based on Zulu time, there was an unusual effect when the Western Australian government decided to trial Daylight Saving last summer. We effectively ignored it. An 8:00am take-off became a 9:00am take-off but it was still a 0000Z take-off and so we didn’t have to adjust our body clocks at all.
A Few Facts Concerning GMT, UT, and the RGO, attributed to Richard B. Langley, Geodetic Research Laboratory, Dept. of Geodesy and Geomatics Engineering, University of New Brunswick, Canada
Another point (that may have been alluded to above) is that when local time switches by an hour to (or from) Daylight Saving Time, this is accomplished by actually switching the time zone.
In other words, for Eastern Standard Time (EST), local time would be reported as 0000 R (Romeo). When the clocks are moved forward by an hour in the spring to Eastern Daylight Time (EDT), our local time was reported as 0000 Q (Quebec), which is the standard time in Halifax. (I hope I didn’t screw this up–for some reason, I thought we switched from Romeo to Sierra, but I must be misremembering this.)
Also, the clocks of most U.S. Navy ships are switched to follow the standard time of whatever time zone they are in. So as a ship transits across the Atlantic, the clocks are continuously adjusted. For U.S. submarines, however, once we submerge, the clocks are generally switched to Zulu time. After all, once a sub submerges, it really doesn’t matter what time it is up above. Submarine OODs (Officers of the Deck) have to make a point of verifying what local time is before going to periscope depth. It’s nice to know in advance whether it’s day or night on the surface.
If I remember right, JAG also uses ‘zulu time’ incorrectly. I’m not a regular watcher, but I seem to remember an episode where the timestamp said something like 0730 zulu time, and it was meant to indicate that it was early in the morning and military folks were already in the office, at work. But 0730 zulu time would have been the middle of the night and it would have been dark out.
Unfortunately, I have no cite to back that up.
