How to use the Rules module to unset all flags (set x days ago) without using Rules Scheduler
Create a page and use whatever content type you want for it, eg. "Article". And assign a path to that page also, e.g. on \admin\dummypage. It doesn't matter what the content of that page is.

Then create a rule (using Rules) and enable the Path Rules module also. With this combination you can trigger a rule when the page \admin\dummypage is visited.

The rule can do (= perform a Rules Action) what you want to do. Built a view and with the help of VBO you can apply the changes you want. See therefore the video mention in the next answer.

Then you have to make sure that the page is visited. You can do this by either of following ways:


Put a reminder in your calender that includes the URL of your special page, and click on the page.
Use a websites like http://www.montastic.com/ (they will retrieve this page regularly).
Schedule a cron job. In this cron job you do a wget statement to retrieve the page and send it to null.