I'm on GMT as well - uhh pretty much the same as John though, in that my sleeping pattern SURE IS CRAZY and I can't really predict when I'll be online but count on it being OFTEN!!! :>
Oh I should say here, my parents have been way stricter with what time I go to bed lately, so I won't be about much later than midnight in GMT time.
For the next three days or so my rents are going away though, so I might just switch to American time and sleep when you all do because I have no life.
I dont know the abreviation or anything, but i think its central something. I live in Texas and sleep exactly never so my patterns actually tend to involve me being up late-night to noon england-time. Which i know because i have too many euro-buds. Oh who am i kidding you cant have too many euro-boobs-*shot*