Why ZULU time? [Archive]

Flypuppy

20th Jun 2001, 14:51

'cos there are 24 time zones, named Aplha to Zulu, excepting India and Oscar (they look too much lie a 1 and a 0 respectively) and the zones go around the globe clockwise. This means Paris and Berlin are in Alpha time etc etc. GMT is the last on the list. QED Zulu time.

mad_jock

20th Jun 2001, 14:51

It's a military term.

Zulu i think is used because it stands for zero difference to GMT and on the radio you would use it to insure that there is no confusion in start time ie 1800 zulu

MJ

wild turkey surprise

20th Jun 2001, 14:52

it's from the old way the world time zones were defined.

24 hours in the day = 24 time zones and they were all given letters of the alphabet (i don't know which two letters were not used).

most of continental europe being 1 hour ahead of gmt was known as 'A' (alpha) time and 2 hours ahead 'B' (bravo) etc etc until you get back round to gmt which was called 'Z' (zulu) time.

hope that makes sense.

[This message has been edited by wild turkey surprise (edited 20 June 2001).]

The man formerly known as

20th Jun 2001, 15:02

Well well.

Does than mean Zulu time predates GMT? When was it invented.

Does it also mean Australia is on India Time? (+9 hours)

wild turkey surprise

20th Jun 2001, 15:08

1)no, gmt and zulu go together. utc is the new name for gmt.

2)no again. see flypuppy above

mad_jock

20th Jun 2001, 15:40

That must annoy Sydney being on Kiwi time :)

Who thought up this UTC crap anyway? I am presuming the french as they have been wanting to move 0 deg long for years.

MJ

[This message has been edited by mad_jock (edited 20 June 2001).]

[This message has been edited by mad_jock (edited 20 June 2001).]

chiglet

20th Jun 2001, 20:59

Alpha is "local" time
Zulu is GMT [noe UTC]
Now since FPLs are filed with eet's then I don't think that the difference is [that] important, but I could be wrong..It has been known, honest
we aim to please, it keeps the cleaners happy

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chiglet

[This message has been edited by chiglet (edited 21 June 2001).]

pigboat

21st Jun 2001, 04:53

mad_jock, you may be onto something here. Just what is UTC, and why was it changed from GMT. Also, who was hector pascal, and why is he different from a millibar?

[This message has been edited by pigboat (edited 21 June 2001).]

FurryDice

21st Jun 2001, 20:14

Wonder if the French will be able in 10 years to get the Euro re-named the ummm Franc?

chiglet

21st Jun 2001, 21:05

MJ et al,
"Zulu" is 'normal' GMT time. Not "summer, double summer" or owt else. Why "Zulu"? I know not. Why UTC? Universal Time Constant put forwards by our European fiends [no spelling mistook]
Why "Zuku"? To keep tack of long haul a/c in the 50's/60's taking ages to cross the Atlantic and they had to have a base line.
If you think of a better explanation please tell me. :
we aim to please, it keeps the cleaners happy

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chiglet

[This message has been edited by chiglet (edited 21 June 2001).]

[This message has been edited by chiglet (edited 21 June 2001).]

IanBowden

22nd Jun 2001, 00:54

Blaise Pascal was some bloke who studied air pressures and the localised constant change of them.

Don't know 'owt about any Hector though, maybe another one hence a combined name, or maybe i am talking s**** again.

Bye,

Ian

Tinstaafl

22nd Jun 2001, 01:30

Well...what else are you going to call 'Zulu'?

'Mervin'? 'Clarabelle'?

"....screech......crackle.....estimate XYZ 0612 Mervin....crackle"

:) :)

FlapsOne

22nd Jun 2001, 01:51

Alpha is only local time if you live in a zone that is 1 hour ahead of zulu.

Yes FPLs use eet but it's darned important that you get your departure time right =zulu.

I always thought utc was a french phrase - Universal Temps Co-ordinee (or something like that).

Hector pascal is, of course, exactly the same as a Millie Bar ......but i still don't know who he is! (drag artist perhaps?).

Mycroft

22nd Jun 2001, 02:09

Pigboat
wrt pressure
pascal is a derived SI unit and is defined as 1 newton per square meter. As this is a very small pressure then atmospheric pressure = app 100 000 Pa. This was defined in the past as 1 bar. Unfortunately neither bar nor pascal is a realistic scale for human perception, so it was decided to use 1/1000 bar (= millibar). Under SI international measurement regulations, every unit should be derived from the 3 defined units of kilogram, metre and second. This means that bar is the official unit of pressure, but 100 Pa being a more usable unit, pressure is stated in hecto (=100) pascals. From the above equivalence of 100 000 Pa = 1 bar then 1 hPa =1 mb, so they are exactly the same, just that hPa is an SI unit; mb isn't. UTC is time at 0º; which of course is the same as GMT but more 'politically correct' as it does not refer to a specific geographical location

pigboat

22nd Jun 2001, 04:25

Thanks mycroft. I was pretty sure that logic had taken a back seat to bull s**t when both terms came into being.

chiglet

22nd Jun 2001, 11:56

Flaps,
A slight correction. "Alpha" is 'standard LOCAL time', ie the time that you set on your watch when in Spain, Greece or where ever
we aim to please, it keeps the cleaners happy

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chiglet

The man formerly known as

22nd Jun 2001, 12:20

Tin..

Mervin or Clarabelle would be interesting. But why not just GMT.

I am sure you can fly across the atlantic on GMT and be able to standardise your arrival and departure times just as easlily as with Zulu.

Why have three names for the same thing Zulu, GMT, UTC, or are they subtly different.

I assume GMT predates the rest of them. Why and when were UTC and Zulu added?

Don D Cake

22nd Jun 2001, 14:03

This may be complete bullsh!t but anyway....

UTC stands for Unversaile Tempes Coodinaire (isn't temps weather?). It's French because the United Nations apparently reckon that French, not English, is the international language. That's why we use SI (Systeme International) units. UTC replaced GMT in 1986, probably purely a political thing.

In the late 1700's an American sea captain named Nathaniel Bowditch published a book " The American Practical Navigator". In it he proposed dividing the world up into time zones. He designated the zone 7.5 deg each side of 15 deg east of the Grenwich meridian "A", 7.5 deg each side of 30 deg east "B" etc. When he got to the International Date Line he realised that although the time was the same either side, the day was different so this 15 deg zone was split into two zones. Hence he proposed 25 time zones. He omitted to use the letter "J" as this letter was considered to be uncommon to all languages. He chose "Z" for the Greenwich time zone simply because he did.

I would hazard a guess that the use of "Z" as an abbreviation for GMT came into widespread use as radio telegraphy evolved.

Zulu time, GMT and UTC are all the same, take your pick.

Don

FlapsOne

22nd Jun 2001, 16:32

Can't agree chiglet

zulu=utc=gmt. plus 1 hour = alpha. plus 2 hours = bravo etc.

There are 24 letters in use (excludes india and oscar) to represent the 24 hours of earth rotation.

We, in UK, are currently using alpha time. When the clocks go back in October we will use zulu time.

Local Time is just that LOCAL TIME, whether it be zulu, alpha, bravo or whatever. Simply re-setting your watch doesn't make it alpha!

18greens

22nd Jun 2001, 20:21

Does that mean India time does exist?

chiglet

22nd Jun 2001, 22:07

Flaps,
When in Oz, I was "assured" that 'local' time was "Alpha". Was it Bullsh*t or what?
we aim to please, it keeps the cleaners happy

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chiglet

matspart3

22nd Jun 2001, 23:58

I'm sure someone once told me that the phrase UTC replaced GMT as the international standard because the clocks which were/are used to 'set' international time were changed. I think some dodgy 50's technology 'Atomic' monstrosity at Greenwich was replaced by half a dozen microchips and a few wires in Paris. C'est la vie!

Tinstaafl

23rd Jun 2001, 00:02

That's my understanding re the change in terminology from GMT to UTC: There was a change in the method of measuring the time standard.

I think it went from star based measurement to caesium clock or something like that.

chiglet

23rd Jun 2001, 00:43

GMT aka UTC aka ZULU. all the same.
"Greenwich MEAN Time". The "central Meridian"
THE line of Longitude. ALL clocks are set by it, hence GMT. Zulu was the Military/Civil ATC nomeclare. Alpha is "local" time. A few years ago, GMT was changed to UTC. At least the beggars couldn't move the Meridian :)
we aim to please, it keeps the cleaners happy

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chiglet

PaperTiger

23rd Jun 2001, 01:22

India Time runs through the middle of Australia. India is in Echo Time, Echo Time.

There are 25 zones (no Juliet). Going East from Zulu they are A, B, C etc, going West they are N, O, P and so on. They meet at M/Y. The use of Alpha to mean local time is wrong, but widespread (probably coined by a journo). However since it is vacant, I propose that henceforth local time be referred to as Juliet :)
http://www.lightshift.com/Vital/Images/timezone.jpg

A Very Civil Pilot

25th Jun 2001, 00:25

GMT was always measured by the Royal Observatory at Greenwich with a load of super accurate atomic clocks(although I think it is now physically in Cambridge.

Sometime in the 60's or 70's the French developed an even more super accurate atomic clock, and as their government were prepared to fund it, they became the timekeepers for us all. Obviuosly the name GMT had to go, so UTC was born - Universale Tempes Coordinatees.

However if you ask someone not involved in the aviation/maritime industtry what UTC is, they will probably tell you it is a type of long-life milk. GMT still rules among the great unwashed!!!!

A Very Civil Pilot

25th Jun 2001, 00:35

Is it just my computer that is playing up, or has the whole of my last post become a link?

_______
"Zulu's, bloody hundreds of them"

chiglet

25th Jun 2001, 01:17

OK clever clogs,
What happens when BST stops? Is it "Zulu" or "Alpha"? And who invited Micheal Caine, eh?
we aim to please, it keeps the cleaners happy

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chiglet

PaperTiger

25th Jun 2001, 02:10

Zulu is always Zulu, it doesn't change with the seasons. If you happen to live in the Zulu time zone (ie the UK), your watch is one hour in advance under BST. You are still in Zulu.

Mooney

25th Jun 2001, 18:05

Some thing wrong with that map......

hmmmmm the pink bit's aren't coloured in :)

Stan By

27th Jun 2001, 04:52

Chiglet,
In BST our watches are showing Alpha time. During winter our watches are shoing Zulu time. The time zones are constant, but UK local varies. That's why the ops room clock (always at zulu) varies compared to your watch.

On another tack, they say we have to change the clocks to suit the farmers. Why don't we use Alpha as local all year, which I think a lot of people would agree with. Those farmers with any animals left can get up at 4 instead of 5, and go to bed at 9 instead of 10. I don't insist the world gets an early night when I'm on earlies!!!

FishHead

27th Jun 2001, 11:31

the man formerly known as....

Downunder has three timezones on the mainland during winter. West Oz is on 'H' (+8), South Oz and the Northern Territory are on 'IK' (+9.5 - hence halfway between India and Kilo), and the East Coast is on 'K' (+10).

When summer rocks around though, we get 5 timezones. The changes are that South Australia (but not the Northern Territory) goes to 'KL' (+10.5), and Tasmania, Victoria and New South Wales go to 'L' (+11).

It makes for fun cross country flying with multiple stops :)

(Of course, if you really want to be technical, we also have Cocos Island on 'FG' (+6.5), Christmas Island on 'G' (+7), and Norfolk Island on 'LM' (+11.5) - so I guess that makes 8 timezones as far as aviators are concerned)