Apparently the status has been "red" every day since December 1st: https://status.github.com/messages/2017-12-07 "The status is still red at the beginning of the day" Yesterday was the first "normal" day, before this outage.
That was different before. They likely changed some historic data when they put the current issue online. Probably just pushed out a quick update.
I've worked on numerous enterprise git servers - they all inevitably go down for at least a half day every 6-9 months.