What Glee says in this thread here: http://boards.straightdope.com/sdmb/showthread.php?t=469779&page=2#post9853072
Got me wondering about GMT.
Since England is obviously in GMT, does GMT change with DST? Or is GMT always the same and England (and most other countries in the GMT-range) gets a GMT+1h in summer?
The reason I´m asking is cause we don´t do DST here, but are in the GMT-zone. So would we be the “only” ones with GMT in summer, while England doesn´t?
I hope that made sense.
England switches between GMT and BST - British Summer Time - which is an hour ahead of GMT.
Thank you for the really quick answer!
Except I think that it’s UTC, rather than GMT - even though they are, for ordinary mortals - the same thing.
Looking at the map on this page:
It looks like there are parts of West Africa that are on or near the prime meridian, and don’t use DST, but I think they may use an offset time anyway.
The UK uses GMT between October and March. In the summer we use BST, as mentioned. So no, GMT doesn’t change: during the summer months, the UK is one hour ahead of GMT.
Similarly the military uses Zulu time which never changes. A letter is assigned to every time zone. GMT happens to be Z. In various reports and orders time is given in Zulu since different time zones may be effected in the same order. Zulu never changes. When writing such an order you always have to take into account if your local time is uding DST and plan accordingly.
And to hijack my own thread then (since the first question is answered) - GMT is the same as UST as well as Zulu time, right?
And thanks again, **PaulParkhead **and Mangetout
I see that the Republic of Ireland is officially UTC+1, switching to UTC in the winter. I guess you’d call that Daylight Wasting Time. Or Darkness Saving Time. That must be unique?
Ok - that answer wasn´t there when I posted my hijack.
Now all things are clear regarding DST, GMT, BST, UST & Zulu.
Really nitpicky question: when they add these “leap seconds” to the year every so often, does the military do the same? I can’t imagine them not doing so since otherwise they’d be a few odd seconds off from everything by now.
There are 24 time zones but 26 letters in the alphabet. Which letters do they skip?
I think it’s called “Making Sure Nobody Calls It ‘British’ Anything Time” 
They skip J. I have no idea why they picked that letter. Julliet can be used to state local time, regardless of where you actually are. However, in the military that is almost never used (I threw it in a couple of operations order to see if anyonw was paying attention). Usually the time will say “zulu” or if it is local it will use the word “local” as in “1800 local”.
Isn’t UTC-12 hours the same as UTC+12 hours?
Only if date doesn’t matter.
If its 0900 Friday UTC then -12 is 2100 Thursday, +12 is 2100 Friday.
To amplify a bit, there are 24 time zones around the world. One though, the one surrounding meridian 180 (the International Date Line) is split into two parts to account for the day change. The west half is ‘Mike’ and the east half is ‘Yankee’ That uses 25 letters. The letter skipped, ‘Juliet’ as Loach says, designates local time.
Here is a time zone map should make the lettering scheme a little clearer. Note that the ‘official’ time zone meridians are marked at the bottom of the map but the actual time zones stray this way and that due to political or cultural reasons. For example despite stretching across four time zones, China is all on Beijing time. Must make sunrise and sunset times a bit odd in western China.
One of the things I took care of when I was in the Navy was the station time standard which, among other things, drove the cryptologic gear. It was crystal-driven and (naturally) was set to Zulu. Once a day or so it would be checked against the time signals from WWV and we used a chart to figure the propagation delay from Ft Collins CO to the site.
Anyhoo, one day a story came in about our station in Homestead, Florida tasking a guy with setting all the clocks ahead when daylight savings time rolled around. He included the station time standard. About a year later somebody rotated in to where I was and was being introduced around. The name seemed familiar so, before I could stop myself, I asked “Are you the guy who put Zulu on daylight savings?” He hung his head and mumbled, “Is that story going to follow me for the rest of my career?”
“Yes — and one hour beyond.”