Can anyone explain why it is that while there are five hours difference in time between New York and London, there is only four hours difference in ZULU time between them, when ZULU time starts in Greenwich just outside of London. Vernon Brown

Hi Vernon,Could it be that ZULU time doesn't care about DST maybe?Cheers,

Hi Vernon,The ZULU time difference between London and New York is (always) 5 hours.The 4 hour difference you're referring to occurs as a result of the Daylight Saving Time scheme, but only for a very short time(of about a week) during the year.Why? Well, in summer, clocks in the UK are set forward by 1 hour during the period from the last Sunday in March to the last Sunday in October. A similar change is made in the US, but the timeframe is from the 1st Sunday in April to the last Sunday in October. So, the only period during which there is 4 hour difference between London and New York is from the last Sunday in March to the 1st Sunday in April of any particular year.You'll find a timezone map here: http://aa.usno.navy.mil/faq/docs/world_tzones.htmlBR,Frank

Sorry Frank but the previous poster was correct, GMT / ZULU is not affected by DST at all and so when daylight savings comes into affect you are out by 1 hr till DST ends. Its a pain as my flying roster is always in GMT which causes major problems when setting the old alarm clock for those early starts!RegardsKris

Reminds me of my time in Iraq - all our watches had to be set to ZULU time (in order to coordinate operations) whereas our body clocks were operating in CHARLIE time.James

"the previous poster was correct, GMT / ZULU is not affected by DST at all"That's what I said, Kris! Quote: "The ZULU time difference between London and New York is (always) 5 hours." :-)The 4 hour time gap is between British Standard Time and US Eastern Time, when they are temporarily(hah!) out of sync.BR,Frank

It is misleading to say

Hi Wolfgang,Yes, of course! I don't know why I put it like that.:-( Your mail makes things very clear.Apologies for compounding the confusion.BR,Frank

Thank you everyone for your kind replies, especially Frank for your Time Zone chart which is very useful as I frequently fly my 737-900 internationally.. I am well aware that there is a five hour difference between "Q" (thank you Frank) and GMT, the problem was that when I went to set the correct time in FS9's clock it insisted there was only a four hour difference! Maddning! Well, we all know Murphys Law (Sod's Law to some of you), and now that I have gone back and retested it sure enough the correct spread is now there, so it looks as if all is well once again.... Vernon Brown

Hi Vernon,You're welcome!I see you live in Greenwich, CT. How appropriate!! :-).BR,Frank