5-day pants rule 

In a college environment, a student's wardrobe is governed chiefly by the "5-day pants rule" (FDPR). The FDPR states that any student may wear the same pair of pants no longer than 5 consecutive days, after which they must change pants and shower. Most new college kids perceive this as excessive, and are new to the idea of not showering every day, but Sophomores and beyond know the need for this rule.

"Hey man, 5-day pants rule, and they've been rank since you spilled milk on day 3."

"Ahh, you're right. Better go change up."

5-day pants rule by Justin Briggs 1984 October 22, 2006