Trigger rule based on time of day

Is there a way to trigger a rule on a schedule.

Basically I have a rule to trigger an email alert then adds the offending machine to a user defined groups, as to not continue to get the alerts. But I want to reset the user defined group on a daily basis, therefore I can get the rule re-triggered if the correlations match again.

However we do not have a good correlation to trigger the reset, so I want to basically clear the group every day at midnight.