Square Root Day occurs this year on the 5th of May. It’s the day on which the square root of the last two digits in the year (2025) is both the month number and the day number.
The last Square Root Day was the 4th of April in 2016, and the next one after this year will be the 6th of June in 2036. For more information about this mathematically special day, see here.
In certain countries, dates are formatted D/M/YY, so this year’s Square Root Day will occur on 5/5/25.
In biodiversity data, Square Root Day will occur on 2025-05-05, following the international standard (ISO 8601) format YYYY-MM-DD.
If the dataset you’re sharing with the world has its dates in anything but YYYY-MM-DD, you are making unnecessary trouble for anyone who wants to use your data. Please stop.
Robert Mesibov (“datafixer”); mesibov@datafix.com.au