Table of contents |
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Introduction |
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Determining the Year |
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Looking at the 1300s |
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Checking 1390 |
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The Correct Date |
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Conclusion |
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In 2001, on October 2, the date in MMDDYYYY format was a palindrome, meaning it reads the same forwards as backwards - "10022001". But what was the last palindrome date before this?
Since one year can only have one palindrome date, the year for the last palindrome date must be before 2001. We can rule out any year in the 1900s because they would result in a day of 91. The same goes for years in the 1800s down to the 1400s.
The last palindrome date must be in a year in the 1300s. At first glance, the 12th month seems like a good place to start, with the latest date being 1321. However, we need to find the maximum year in the 1300s with a valid date.
Let's consider the year 1390. The date would be 09/31, but is this a valid date? Unfortunately, no - September only has 30 days. Therefore, the last palindrome date must be before September.
The latest date before September in the 1300s with a valid day is August 31st. Therefore, the last palindrome date before October 2, 2001 was 08/31/1380.
By analyzing the number of days in each month and the years in different centuries, we were able to determine the last palindrome date before October 2, 2001.