Its a Perfect Square
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https://www.npr.org/2025/09/16/nx-s1-5535545/pythagorean-triple-square-day-9-16-25
Once a century, a very special day comes along. That day is today — 9/16/25.
Pi Day (3/14) often comes with sweet treats; Square Root Day (4/4/16 or 5/5/25, for example) has a certain numerical rhyme. But the particular string of numbers in today's date may be especially delightful to the brains of mathematicians and the casual nerds among us.
First, "all three of the entries in that date are perfect squares — and what I mean by that is 9 is equal to 32, 16 is equal to 42, and 25 is equal to 52," says
Next, those perfect squares come from consecutive numbers — three, four, and five.But perhaps most special of all is that three, four, and five are an example of what's called a Pythagorean triple.
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Maybe Sept 16, 2025 was not so special after all.
Saturday, September 27, 2025, is a very special day–mathematically speaking. That’s because the date’s numerals combine to form a rare numerical trick that even the most ardent math hater will appreciate.
If you write out September 27, 2025 as 09/27/2025 and eliminate the forward slashes, you get 9,272,025. The notable thing about that number is that it’s the square of 3,045. In other words, 3,045 times 3,045 is 9,272,025, as Fresno State University math instructor Howie Hua explains in a social media video, describing it as the “coolest mathematical date of our lifetime.”
But wait, there’s more! As you probably know, people in some countries write their dates out with the day before the month. In that case, 27 September, 2025 would be 27/09/2025. If we run the same trick as before, 27/09/2025 turns into 27,092,025. Lo and behold, that is the square of 5,205—5205 times 5205 is 27,092,025.
According to Timeanddate, this means September 27, 2025 isn’t just a square date, it’s a global square date, which occurs only eight times this century.
