My mother shoved a satisfyingly thick fengshui book for the year into my face the last time I went back home.
It lists, among other things, days that are 忌 (contraindicated) for certain activities.
There was one whole page on things to do with your hair!! Like, cutting, dyeing and WASHING hair even. Best, there was one month with three consecutive days where you're not supposed to wash.
Welcome to the year of the Dirty Rat.