Frostmourne is about 15-16 (daylight savings confuse me sometimes) hours ahead of that PST time Blizzard always uses to announce server restats/shutdowns.

They say 5am, which is 8pm for me which is either 10 or 11pm for server depending on DST.

PS: Frostmourne is the best :P

PPS: All Oceanic severs have the exact same time I think.