Replying here as I suspect the information will be helpful to multiple people.
I suspect the problem is the server localization setting. Double check with your host that the timezone is properly configured and that you know the server’s timezone. And that it’s entered correctly in EE!
I believe it’s working for the moment as I overrode the default session length by adding these two variables to the config file:
$config['user_session_ttl'] = '72000'; // 7200 2 hours
$config['cp_session_ttl'] = '72000'; // 3600 1 hour
So- I upped the session length to 20 hours, which is a bit extreme. Heh. But it’s a quick and easy way to confirm that the problem has to do with the session length being cut off due to confusion as to what time it is now. And that confusion is most likely due to an issue with the server tz settings- either on the server level, in EE, or both.
Make sense what’s going on there? Double check those settings and hopefully a tweak there eliminates the need to set the long session length.