Today's date is rare, and it's not just because it's a palindrome.
Dec. 2, 2021, written out numerically as 12/02/2021, is a palindrome because it reads the same backward as it does forward. But what makes Thursday's date extra uncommon is that it can also be read upside down just the same.
If you drop the slash marks from today's date and punch it into an analog calculator, you'll get the same image no matter which way you view it: upside down or right sideup.
Tyler Roney, a meteorologist in Sioux Falls, South Dakota, displayed the ambigram on Twitter, but it might require you tilting your head to the side or flipping your phone upside down to see it both ways.
🚨 Nerd Alert 🚨
Today’s date is not only a palindrome (the same front to back) but it’s also an ambigram which means it’s the same upside down as well! pic.twitter.com/f3IuAV2boR
— Tyler Roney (@TylerJRoney) December 2, 2021
That's not all.
Thursday marks an eight-digit palindrome, which occurs only 12 times this century. The next one doesn't come until March 2, 2030, spelled out numerically as 03/02/2030.
That's according to Aziz Inan, an electrical engineering professor at the University of Portland who has tracked the dates for years.
He told the Farmer's Almanac that 2021 has 22 palindrome dates of at least four digits, which won't happen again for 90 years, in 2111.
Today's rare palindrome comes toward the beginning of a long stretch of such dates to kick off December. The month starts with nine consecutive palindromes of at least five digits, beginning with 12/1/21 and ending with 12/9/21.
That comes after a run of 10 palindrome dates in January, which was headlined by the first palindrome date to fall on Inauguration Day, according to the almanac.
Follow Jay Cannon of USA TODAY on Twitter: @JayTCannon
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This article originally appeared on USA TODAY: Palindrome, ambigram alert: Dec. 2, 2021, is a doubly rare date