Yes, I'm a newbie

I know about Thurs night maintenace & I'm happy to work around it but I give up trying to work out the time differences. I know the maintenance happens 10.30pm every Thurs night GMT for approx 4 hours, but it's 10.30 pm Friday here & I still can't get on - I keep getting an error message. I think I need to allow an 11 hour difference (?) but it doesn't work out. ... or am I working too many late nights?
ciao, Elena