I don't know if it is a Royal requirement, but our previous proclamations had a specific date on them when we received them from the Gov. office. So they were self limiting.
Now Minnesota has a blanket proclamation good for the rest of present governors term of office.
I am not that Dr. , but was presumptuous enough to interject my 2 cents worth anyway. :)
Carlyle, KCBS, CBJ, Organizer ( Judge Chair)