O365 makes sense if it's down all day, since this is a leap year, after all.
The exact-ish length of a year is 365.2422 days. 365 days a year is three nines of uptime (99.93369%).
In 10 years it'll be Office 404
Edit: maybe not that short, in 20, 30 years maybe?
39 is my guess.
365+39=404
They didn't call it O365/24/7 for a reason.
1990s hosting company: Linux Server 99.99% uptime. Windows - no guarantee. 2020 - same
This is the first time since 2015 that I remember an outage of this magnitude (scope + impact) with the platform. Not saying my memory is authoritative, but.. I certainly wouldn't call this regular.