I dont see a way to do that easily via the UI.
You could make a filter similar to this:
name: afterhours
execution order: 1
Filter Status: disabled
Target Channel: emails
Filter rule: User / Email Address - Contains - @
Filter Actions
---> Send an Email (with recipients: %{user})
subject: closed
body: we are closed right now
---> Disable autoresponse
Then using a scheduler you could enable the filter at 16h and disable it at 9h (or whenever you want). The scheduler would run a script to execute a mysql command something like:
To enable the rule
UPDATE ost_filter SET isactive=1 WHERE id=#'
and
to disable the rule
UPDATE ost_filter SET isactive=0 WHERE id=#'
Where # is the filter rule id. Alternatively you could also match by name WHERE name='afterhours'
.
You would of course need a username/password to connect to the database and issue the command.