Connection : 20th of the month.

Bear with me.

According to this : https://allthatsinteresting.com/it-was-a-good-day-actual-date

Today was a good day took place on the 20th of Jan, 1992. 4/20 weds is for the 20th of april 2005, because Fantomas decided to make a calendar album. Both songs are based on the 20th of their respective months.