PlanetSide 2's case. SOE producer David Carey recently took to Reddit to explain why the MMOFPS' server downtime typically starts during European prime time.
PS2 is a worldwide game, Carey says, and so bringing the EU shards down independently isn't feasible. "We can't have multiple client or server versions out in the wild at the same time," he explains. "Another reason is that we update once a week or more on average," Carey continues. "We need people to run the patches, so we really can't just say 'hey you guys are working overnight tonight and maybe two other nights this week, we'll let you know.' I mean, they have families and that's just not fair. So that rules out some time slots like 2:00 a.m. local other than for emergencies."