Hello
I'm entering the correct format but whatever I try I get "You have to specify a valid date."
Even put in a date picker but still get the same issue. Have tried changing the Scheduler date format but even that doesn't make a difference. Also checked the Date and Time format on the Admin - Settings but can't see anything there.
Guessing it compares with a system date which is maybe using a different date format?
example
Unpublish on:
Found problem
Not sure is part of the core files and therefore always there (not likely as I did go through most things looking for expirey dates), or whether the Expiration date was added to the element upon enabling something. Anyway found in publishing options on the node (page in this case below) expiration date with a pre-populated date. Removed this and scheduler worked.
Publishing options