The plugin adds a “Start date” field and an “End date” field to the products. You can enter your special price as usual and then fill in these two fields. In the frontend, the date until which the special offer is valid is now displayed under the special offer.
Once the date has been reached, the plugin copies the special offer price into the “Lowest price in the last 30 days” field, inserts the normal price again and removes the start and end date.