Why are the statutory holidays on wrong date?

[AC Question]

Hello - All of the statutory holidays show up in the calendar on the day prior. Example: Labour Day in Canada is actually September 7th this year and it shows up on the SUnday prior. I have tried to change the date, but when I reopen the calendar the stat defaults back to the original incorrect date.
It has been the same for every statutory holiday this year.
I appreciate your help.
Michelle