# 11-02-2011: Only palindrome day for a century

This is a special one-of-a-kind calendar palindrome day: Wednesday, November 2, 2011, expressed as 11-02-2011 (or simply, 11022011)!

What makes this palindrome day so special, one-of-a-kind? Well, please read the article I recently published in the University of Portland weekly student newspaper The Beacon.

In addition to the article, here is a list of more reasons as to why November 2, 2011, is indeed a rare special palindrome day:

- Did you know that among all the palindrome dates contained in this (21st) century (38 total), 11022011 is the only one to occur in November! (Note that the month of November is a palindrome month since it’s the 11th month of each year.)

- Last time a November palindrome day occurred was 100 years ago on November 9, 1911 expressed as 1191911! (Note that this is a seven-digit palindrome day which can also be interpreted as the full date number of January 19, 1911 if written as 1-19-1911 instead of 11-9-1911. This was the only November palindrome day that occurred in the 20th century.)

- November 2, 2011 expressed as 11022011 is an eight-digit palindrome date. Eight-digit palindrome dates occur much more seldom. Amazingly, last time an eight-digit November palindrome date occurred was 800 years ago on November 21, 1211 written as 11211211! Note also that the last November palindrome day that occurred in the day-month-year date format used by the rest of the world was 819 years ago on 29 November 1192 written as 29111192! Isn’t that something?

- The November palindrome day that occurred before 11211211 was the utmost unique eight-digit palindrome day 11-11-1111 (that is, November 11, 1111) which is made of all the same digits! No such palindrome day will occur again until the year 11111 on November 11 (that is, 11-11-11111, involving nine same digits)! (Note that as far as palindrome dates made of all the same digits, February 2, 2222 expressed as 2-2-2222 (six digits) and February 22, 2222 expressed as 2-22-2222 (seven digits) are the nearest ones to occur in the 23rd century.)

- After November 2, 2011 (11022011), the next two palindrome dates to occur in November will both be in year 2111. These dates are November 1, 2111 (1112111, involving seven digits) and November 12, 2111 (11122111, involving eight digits). In fact, these are the only two November palindrome dates to occur in the 22nd century.

- 23rd century also contains two November palindrome days: November 2, 2211 (11-2-2211, involving seven digits) and November 22, 2211 (11-22-2211, eight digits). Note that 11-22-2211 will be the last eight-digit November palindrome day to occur in the 3rd millennium.

- No November palindrome days in day-month-year date format will occur in this (21st) century! However, the 22nd century contains nine November palindrome dates in day-month-year date format, the first one being 1 November 2111 (1112111) and the last 9 November 2119 (9112119). After these nine, no more November palindrome days in day-month-year date format are to occur in the 3rd millennium. Wow!

- Interestingly enough, 1102 (which represents November 2nd) can be expressed in terms of its prime factors in a palindrome fashion as 29 x 19 x 2 (that is, 29192 without the multiplication signs).

The following table lists all the November palindrome days between the 17th and 26th centuries:

November 6, 1611 11-6-1611*

November 7, 1711 11-7-1711*

November 8, 1811 11-8-1811*

November 9, 1911 11-9-1911*

November 2, 2011 11-02-2011 (eight digits)

November 1, 2111 11-1-2111*

November 12, 2111 11-12-2111 (eight digits)

November 2, 2211 11-2-2211*

November 22, 2211 11-22-2211 (eight digits)

November 3, 2311 11-3-2311*

November 4, 2411 11-4-2411*

November 5, 2511 11-5-2511*

*Note that in the above table, the seven-digit palindrome dates indicated with an asterisk could also be interpreted as month of January dates. For example, if calendar date 11-6-1611 is rewritten as 1-16-1611, it corresponds to January 16, 1611 instead of November 6, 1611. The eight-digit palindrome dates only correspond to a single calendar date in the all four-digit years.

I hope all of these facts will convince you about why November 2, 2011, is such a special, rare, one-of-a-kind palindrome day! And aren’t we all lucky to have such a day in our lifespan?

*Aziz S. Inan, Ph.D., is a professor of Electrical Engineering at the University of Portland in Portland, Oregon. **Read more from Aziz Inan in the University of Portland Beacon*

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