Today is September 19, 2019. If this is written out in m-dd-yy form (the American way; apologies to all non-Americans), it reads 9/19/19. This number, 91919, is a palindrome - a number that's the same forwards and backwards! The last nine days have all been like this - 91019, 91119, 91219, etc. This has been referred to as a Palindrome Week. Although it's 10 days, each day of the 'week' is a palindrome, which is where the name comes from. Tomorrow, unfortunately, will be September 20, which won't be a palindrome. That will thus mark the end of 2019's palindrome week. If you're feeling sad at the end of this 'week' of palindromic celebration, here are a few dates you should write down in your calendar:
January 20, 2021
This is the next palindromic day on the American calendar, as its written 12021. This will also be the start of the next palindromic week, as the days will be 12121, 12221, all the way up to 12921. For the rest of the 20's, there will be a palindrome week 13 months after the previous one. The next palindrome week will start on February 20, 2022, then March 20, 2023, and so on.
December 1, 2021
The palindromic weeks discussed have been written in m-dd-yy format, but December 1-9 is a palindromic week if written in mm-d-yy format. The palindromes are 12121, 12221, etc., which are the same palindromes as January 20-29, 2021. If written in this format, it will be December's only palindromic week of the century.
September 20, 2029
This will be the start of the last Palindrome Week of the century. Palindrome weeks are 5 digit numbers, so the first number of the year must be the same as the first number of the day. When the 30's begin, the day of the must also be in the 30's. However, a month has at most only 2 days in the 30's. Thus, this will be the last palindromic week of the 21st century.
September 30, 2039
This will be the last palindromic day written in m-dd-yy format of the 21st century. The next day that can be written as a palindrome in m-dd-yy format is January 01, 2101. Don't forget to mark your calendars!
February 2, 2020
This isn't a palindrome in m-dd-yy format, but is one of only 12 days this century that are palindromes when written in mm-dd-yy format! Three of them have already happened (10/02/2001, 01/02/2010, 11/02/2011), but there are 8 after February 2, 2020. After February 2, 2020 is December 2, 2021. Then, starting on March 2, 2030, there will be a palindromic day every 10 years and one month after the last one. So after March 2, 2030, the next palindromic day will be April 2, 2040, then May 2, 2050, up until September 2, 2090!
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