How to assign a benefit option in a specific date of the year?

The customer asked us to automatically assign a benefit option in certain date of the year. i.e. responsability bonus of a fixed amount on march 15th. The benefit program is configured to begin on Jan 1st and finish on Dec 31th and, throught the year, there will be some options that must be assigned automatically on specific dates.

Is there a way to do this via fast formula or mass upload?