not totally sure, but I had bought Elite on February 25th and including that day it lasts 29 days. I thought it lasts for a whole month and I know it sounds weird as I am complaining for 1 day off 30 days of elite but if I renew it in march it would last for 30 days.
It lats as many days as needed for a full month if you bought it on the 1st, I think this was recently discussed. Though that should be 28 days for feb, maybe it doesnt believe in leap years or something idk.