Palindrome Day
Palindrome Week: May 10 - May 19,
2015 are all Palindrome Days (m/dd/yy).
A Palindrome Day happens when the
day’s date can be read the same way backwards and forwards. The dates are
similar to word palindromes in that they are symmetrical.
Palindromes read the same way
forwards and backwards, like 'BOB'.
Because date formats vary from
country to country, not all dates that are be considered palindromic in one
kind of date format are Palindrome Days in another. For instance, June 10, 2016
or 6-10-2016 is a palindromic date in the month-day-year (m-dd-yyyy) format,
but is not if you write the date as mm-dd-yyyy (06-10-2016); as day-month-year
(dd-mm-yyyy: 10-06-2016) or as year-month-day (yyyy-mm-dd: 2016-06-10).
Different
Digits
In addition to the format, many
people around the world also write the digits on the date differently. For
instance, it is common to write only the last two digits of the year – so, 15
instead of 2015. Other such representations include:
- d-m-yyyy or 10-5-2015
- d-m-yy or 10-5-15
- dd-md-yy or 10-05-15
- mm-dd-yy or 05-10-15
Each of these date formats has its
own Palindrome Days.
Whether a date is palindromic or not
depends on how it is written.
Some
Palindrome Dates are Rare
Depending on date formats,
palindromic dates can be rare. Aziz S. Inan, an electrical engineering
professor at the University of Portland, Portland, U.S.A. has calculated that
in the mm-dd-yyyy format, Palindrome Days tend to occur only in the first few
centuries of each millennium (1000 years). The last palindromic date in the
second millennium (years 1001 to 2000) in this format was August 31, 1380 or
08-31-1380.
According to Dr. Inan, in the
mm-dd-yyyy format, the first Palindrome Day in the current millennium (January
1, 2001 to December 31, 3000) was October 2, 2001 (10-02-2001). The last
Palindrome Day in the millennium will be September 22, 2290 (09-22-2290).
There will be 12 Palindrome Days in
the 21st century if you write your date in the mm-dd-yyyy format. The first one
was on October 2, 2001 (10-02-2001) and the last one will be on September 2,
2090 (09-02-2090).
In the dd-mm-yyyy format, there are
29 Palindrome Days in the current century. The first was 10 February, 2001
(10-02-2001). The last is a special one – it's a leap day! 29 February, 2092
(29-02-2092) will be the last Palindrome Day of the 21st century.
Over
a Week of Palindromes
In 2015, people who write their
dates in the m-dd-yy format will be treated to 10 consecutive days of
palindromic dates. Every day from May 10, 2015 (5-10-15) to May 19, 2015
(5-19-15) will have a palindromic date.
Such an extended period of
back-to-back Palindrome Days in the m-dd-yy format are not that rare. Every
year since 2011 have had 10 consecutive Palindrome Days. In 2011, they occurred
from January 10, 2011 (1-10-11) to January 19, 2011 (1-19-11). In 2012, the same
sequence of dates occurred in February and 2013 it happened in March. In 2016, this will happen in the month of June.
Notice a pattern here? As long as
you write your date in the m-dd-yy format, every century has 9 years with 10
Palindrome Days in a row. These years are always in the second decade of the
century. For example, every year between 2011-2019, 2111-2119, and 2211-2219
will have 10 consecutive Palindrome Days. This is true for previous centuries
as well.
The month this happens corresponds
to the last digit of the year. For instance in 1918, 2018 and 2118, the 8th
month of the year, August, will have 10 Palindrome Days. Each of
these days will begin on the 11th day of the month and end on the 19th.
More
Upcoming Palindrome Days
m-dd-yyyy format
- June 10, 2016 (6-10-2016)
d-mm-yyyy format
- 5 October 2015 (5-10-2015)
- 6 October 2016 (6-10-2016)
