Forget Pi Day. Today is Pythagorean Triple Square Day.

Today is Pythagorean Triple Square Day. September 16, 2025 holds extra special mathematical significance. Breakthroughs, discoveries, and DIY tips sent every weekday. Pi Day (March 14) is a day of global mathematical celebration, but it's not the only numerically significant calendar date. In fact, today marks a special occasion that only occurs once this century.