Hm, your question may be a bit misplaced, this is ment for site and forum related questions..
But since I'm such a nice guy, I'll give you an answer..
As you may know, the world is divided into time zones.
"Zulu time" is also known as Greenwich Mean Time "GMT". (Or "Universal Coordinated Time (UTC)" as it is called today)
A(lpha) time would then be GMT+1 hour, B(ravo) GMT+2 hours etc..
Most (international) military operations are run in Zulu time, to help prevent a time chaos due to the time difference.
Here's some more help from good old google again:
http://www.google.com/search?q=zulu+...TF-8&hl=no&lr=