This is reason #532 or so why we need gigantic libraries to deal with dates and times. "24 hours in a day", "60 seconds in a minute", lol, no.
This time, all calendar events will start an hour late on the week of the 11th if you a) have the week to start on Sunday and b) use the 7 day a week calendar
It's been fun having to communicate this with all my clients.
https://social.technet.microsoft.com/Forums/office/en-US/a43...
Edit: links: