Have you found out if your host recently changed your server's PHP etc
What is the version of PHP.
We have not changed any date stuff in PP8 over any previous version.
I have no access to that site just because I may have at some pointed installed it. It is not like I keep 50000 logins.
I would suspect your host updated your server and its an issue with your specific php version. I would need more info to assist.
Looks to me based on what I am seeing your host has updated PHP on your server and not set the default timezone.