My program required a accurate username and password to present its features to the user, and there is one predefined user who is idle most of the time and does just two things: wipe stale database entries and restore the database when needed. According to my login procedure, each time a user successfully logs in the system automatically updates the last login date to the current date. And that was the hint I desperately needed.

A brief snippet of code is included showing how he implemented the solution - MySQL commands and parameters defined in constants and called only when the last login time is less than "today".