Greenwhich main time or something.
GMT 0 means you live in england, that's the main time.
If you live in a different timezone, your GMT is different.
Scroll down the page, it would say something like "All times are GMT. The time now is 03:54 PM."
Take that time, look how much later/sooner it is where you live and you got it.
Example, GMT 0 is 04:00 right now.
Where I am, time is 05:00
So I got GMT+1