Forex Signals Forecast Question

I know some are not reliable because its really up to you if you would pull the trigger or not. My question is. I saw a lot of Forex signals on the net it says that there signals are based on GMT time … “Euro session”??? I don’t know if he is talking about the start of the london session 3:00 am? ET Time??
this is the example of forexsignal i saw i want to test out this kinds of orders

Friday, 26 November 2010 06:07
EUR/USD

Sell @ 1.3313 ( Stop/Limit/Market Order)

Set Stop Loss @ -40pip
Set Profit Target @ 50 pips

Note: Time here is based on GMT

what i dont understand is what GMT time is he talking about there are many kinds of GMT 1,2,3… 8. . . . . . etc