If it seems like the day to day differences in the length of days is greater now than at some other times of the year, it's not your imagination. It is greater at this time of year.
Variable stars change their brightness over a period of time.
Algol gets dimmer approximately once every 2 days and 20 hours. It stays near its dimmest for about 2 hours, with the entire fading and brightening process lasting about 7 hours. Algol is best seen beginning in autumn and into early winter. It is found in the northern constellation Perseus. See diagram below for graphical representation of Algol's position relative to Cassiopeia.