Back in BPOS days there was a RSS feed that allowed you to subscribe to alerts for system issues/outages and planned maintenance notifications.
This wasn’t originally available in Office 365 but was recently implemented in under Service Health section in the Microsoft Online Portal.
The great thing is you don’t actually need to authenticate against Office 365 to subscribe (once you know the URL) so it can easily be incorporated into dashboards or other RSS viewers such as the one in SharePoint Online.
You can read more at BoxFreeIT: http://www.boxfreeit.com.au/Productivity/how-to-know-when-office-365-will-be-offline.html