Since around midnight a lot of Realms went down and were unreachable. They seem to be back now, according to Realm Status Page but players are still stuck at connecting.
The login screen gives some hint at an emergency maintenance, but of course „Realm Status“ Forum gives no hint. Why do they have the forum if it does not get used? Just because they hope to have the realms back up before the majority of Players gets up today to avoid another reimbursal of play time?
Update: Loginserver is back online and Realms are available since around 09:30