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Old 03-23-2007, 11:38 AM
Spectre of Pithecanthropus Spectre of Pithecanthropus is online now
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In the TV show JAG, why does the word Zulu appear after a time of day?

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?
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  #2  
Old 03-23-2007, 11:42 AM
Bag of Mostly Water Bag of Mostly Water is offline
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Z is the letter designating GMT.
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Old 03-23-2007, 11:42 AM
Captain Amazing Captain Amazing is offline
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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.
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Old 03-23-2007, 11:42 AM
Johnny L.A. Johnny L.A. is offline
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Zulu is used to indicate Greenwhich Mean Time (Coordinated Universal Time).
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  #5  
Old 03-23-2007, 11:42 AM
bordelond bordelond is online now
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Wikipedia to the rescue (search on "time zone"):

Quote:
Time on a ship's clocks and in a ship's log had to be stated along with a "zone description", which was the number of hours to be added to zone time to obtain GMT, hence zero in the Greenwich time zone, with negative numbers from −1 to −12 for time zones to the east and positive numbers from +1 to +12 to the west (hours, minutes, and seconds for nations without an hourly offset). These signs are opposite to those given below because ships must obtain GMT from zone time, not zone time from GMT. All zones were pole-to-pole staves 15 wide, except −12 and +12 which were each 7.5 wide, with the 180 meridian separating them. Unlike the zig-zagging land-based International Date Line, the nautical International Date Line follows 180 except where it is interrupted by territorial waters and the lands they border, including islands. About 1950, a letter suffix was added to the zone description, assigning Z to the Zero Zone, and AM (except J) to the east and NY to the west (J may be assigned to local time in non-nautical applications; zones M and Y have the same clock time but differ by 24 hours: a full day). These were to be vocalized using a phonetic alphabet which included Zulu for GMT, leading sometimes to the use of the term "Zulu Time". The Greenwich time zone runs from 7.5W to 7.5E Longitude, while zone A runs from 7.5E to 22.5E Longitude, etc.
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Old 03-23-2007, 11:48 AM
Papermache Prince Papermache Prince is offline
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Four posts at the same time? What's the record on simultaneous posts?
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  #7  
Old 03-23-2007, 11:49 AM
sciguy sciguy is offline
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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.

Last edited by sciguy; 03-23-2007 at 11:54 AM.. Reason: specified DC so some smart alec won't tell me Seattle is GMT -8
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Old 03-23-2007, 11:51 AM
outlierrn outlierrn is offline
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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.
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  #9  
Old 03-23-2007, 12:08 PM
Richard Pearse Richard Pearse is offline
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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.

Last edited by Richard Pearse; 03-23-2007 at 12:11 PM..
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  #10  
Old 03-23-2007, 12:18 PM
Loach Loach is online now
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Quote:
Originally Posted by 1920s Style "Death Ray"
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.
Juliet can be used as "local time". It usually isn't because it is easier and less confusing to say "1300 local".
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  #11  
Old 03-23-2007, 12:39 PM
Richard Pearse Richard Pearse is offline
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Quote:
Originally Posted by Loach
Juliet can be used as "local time". It usually isn't because it is easier and less confusing to say "1300 local".
I didn't know that. We always just say "local" or very rarely we may refer to "Hotel".
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  #12  
Old 03-23-2007, 12:47 PM
Duckster Duckster is offline
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Quote:
Originally Posted by 1920s Style "Death Ray"
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.
What is universal time from the US Naval Observatory.

Background from Wkipedia.

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
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  #13  
Old 03-23-2007, 12:59 PM
Colibri Colibri is offline
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Quote:
Originally Posted by Papermache Prince
Four posts at the same time? What's the record on simultaneous posts?
I believe I have seen five with the same time stamp.

I think I have seen seven within one or two minutes.
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  #14  
Old 03-23-2007, 01:06 PM
robby robby is online now
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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.
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  #15  
Old 03-23-2007, 01:21 PM
Gala Matrix Fire Gala Matrix Fire is offline
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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.
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  #16  
Old 03-23-2007, 02:14 PM
Johnny L.A. Johnny L.A. is offline
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Quote:
Originally Posted by bluethree
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.
I've noticed the same thing.
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  #17  
Old 03-23-2007, 03:15 PM
Rick Rick is online now
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Quote:
Originally Posted by bluethree
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.
No they didn't screw it up, you just have to remember that:
A sailor may work from sun to sun,
But a lawyer's work is never done.



Yeah, I have seen that mistake also.
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  #18  
Old 03-23-2007, 03:31 PM
Ximenean Ximenean is offline
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Quote:
Originally Posted by Captain Amazing
So, 1430 Zulu means that it's 2:30 PM in London/Paris/that time zone.
Nitpick - if it's 2:30pm in London, it's 3:30pm in France (and even in Spain).
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  #19  
Old 03-23-2007, 04:02 PM
sqweels sqweels is offline
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So is sunrise in Kent what they call "Zulu Dawn"?
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Old 03-23-2007, 04:04 PM
pravnik pravnik is offline
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Quote:
Originally Posted by Rick
No they didn't screw it up, you just have to remember that:
A sailor may work from sun to sun,
But a lawyer's work is never done.
Not if they're billing hourly, anyway.
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  #21  
Old 03-23-2007, 05:16 PM
Duckster Duckster is offline
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Quote:
Originally Posted by Rick
No they didn't screw it up, you just have to remember that:
A sailor may work from sun to sun,
But a lawyer's work is never done.
Is that because for some lawyers the sun shines out their ...

Whut?

Ouch!
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  #22  
Old 03-23-2007, 06:40 PM
Captain Carrot Captain Carrot is offline
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Quote:
Originally Posted by Colibri
I think I have seen seven within one or two minutes.
Even a difference of a minute or two can be a simulpost, since I could post at 2:30:50 and you at 2:31:02; different minute, but still a simulpost.
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  #23  
Old 03-23-2007, 06:53 PM
silenus silenus is online now
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Which then brings up the question: How do you feel when there is a seven-way simulpost to your thread? Pleased that so many people care about your question, or abashed because everybody but you already knew the answer?
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  #24  
Old 03-24-2007, 11:29 AM
SpoilerVirgin SpoilerVirgin is offline
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I'm just amused that Spectre and I have identical viewing habits. When I saw the thread title, I thought, "Ah, someone else has been watching the reruns on USA in the morning." But I had to laugh when I read the OP, because I too was watching the 7:00 a.m. Star Trek while I got ready for work until they pulled it for Sanford and Son, and just this week discovered that I could switch to JAG instead. TV Land is a very small world. And don't feel too bad, I didn't know the Zulu thing either.
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