An unexpected error occurred when attempting to set time settings on page access permissions

Permalink
Good morning,
My concrete5 has just been upgraded to 5.6.1 and now my website is not accessible to the public.
I have narrowed it down to the upgraded advanced site permissions however I am unable to change the permissions because I get "An unexpected error occurred. An error occurred while processing this request" on the section for time settings.
(Permissions --> view --> included vs excluded) I am able to select access but the error is for the time setting of access & therefore I can't save the changes & make my site live again.

See screenshot attached.

1 Attachment