Late?

I have a friend who bought a monthly pass (that came out at the start of the month, and last day to buy it is at the end) today, and my other friend said: "Dude you bought it so late." Isn't this technically not "late" as the deadline is at the end of the month? Is late used differently here (does not refer to deadline)? How do we know when "late" is comparing to something else other than the deadline? Common sense?