A palindrome is a word that is spelled the same backwards and forwards, like toot and racecar. Can you think of any others? It turns out numbers can do the same thing — like today’s date! Today is written as 1/20/21, which means the 20th day of the 1st month (January). In fact, we’re just starting a whole stretch of palindrome days that will last through 1/29/21. Don’t forget, 1/2/21 was a palindrome, too! We’ve been having cool streaks like this for the past few years, like 9/17/19, and 8/12/18…but today is extra special because it works even with the full year: 1/20/2021! Let’s see how often these cool dates happen.
Wee ones: How do you say “123” in backwards order?
Little kids: If you say “221” in backwards order, is it the same or different? How about 454? Bonus: How old will you be the next time your age is the same backwards and forwards?
Big kids: The digits of 1/20/21 add up to 6 (1 + 2 + 0 + 2 + 1). What’s the next date (using 2 digits for the year) with digits that add up to 6? Bonus: Are there any more future dates in 2021 with digits that add up to 6?
The sky’s the limit: If you’re allowed to write both the month and year as 2 digits, when’s the first year when we won’t have any palindromic dates? (For example, in 2030 you can write March as 03).
Wee ones: 321.
Little kids: 221 then reads 122, so it’s not a palindrome. But 454 does work! Bonus: Different for everyone…any single digit works, like 7, 8 or 9! Or your next age might be 11, or 22…or 101!
Big kids: 2/1/21. Bonus: Just 2/10/21.
The sky’s the limit: In 2100. We’ll have palindromic dates in 2022 (2/20/22, 2/21/22…), and in 2023 we can have them in March (3/20/23 through 3/29/23, plus 3/2/23). Then in 2024 we’ll have 4/2/24, 4/20/24, 4/21/24 and so on. That’s true throughout the ’20s, with dates like 5/20/25, all the way through 9/29/29. In 2030 we start over with 03/1/30, then 1/3/31. This pattern will continue through the ’40s, ’50s, all the way to 9/9/99 in 2099. 2100 is the first year we won’t have a palindromic date, because we can’t have 0/0/00!
Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.