Why 27 September 2025 is a Remarkable 'Square' Date
- Editor OGN Daily
- Sep 27
- 1 min read
Fresno State University math instructor Howie Hua says it's the “coolest mathematical date of our lifetime.”
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 those who prefer to give math a skip will still enjoy.
Why? Well, 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.
Underwhelmed? 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. So, 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. The next global square date will take place on January 1, 2036, or 01/01/2036, which feels a bit like cheating since both versions yield 1012036 (1006 x 1006).
Extreme Numbers Get New Official Names: For the first time in more than 30 years, new terms have been officially added to the International System of Units (SI). The four new prefixes - ronna, quetta, ronto and quecto - describe very large and very small numbers that until now didn’t have their own names.