On the palindromic and symmetric characteristics of string representations of dates
Abstract
String representations of dates are limited by very many rules and exceptions in the way we keep track of time. Hence the validation thereof is non-trivial. In this paper, we shall explore the palindromic and symmetric characteristics of certain date strings, and calculate the previous and next occurence of such strings in the linear temporal progression that which we are bound to be in.
Definitions
A string is palindromic if it is the same when read forwards and backwards, disregarding spaces, such as "radar" or "palindromicimordnilap."
A string representation of a date is called palindate if it is palindromic.
A string has rotational symmetry if it is the same after a non-trivial rotation, such as "pod" or "01256895210."
A palindate is a rotatiopalindate if it has rotational symmetry.
The YYYYMMDD Date Format
Today's date in YYYYMMDD format is 2009 01 05.
(N.B. Spaces are added in the string of numbers to aid reading, but they are not considered as part of the string.)
The previous palindate was 2001 10 02.
Anecdote.
This was the day when I was introduced to this palindate game, when Mr. Dahl,
my high school physics teacher from 2002 (whom I knew not at that time) was a substitute teacher for my biology class.
He asked us what was the last palindate (before 2001 10 02), and I incorrectly replied 1321 12 31.
After realizing my error, and before anyone else could correct me, I said 1380 08 31.
The next palindate is 2010 01 02.
Since a rotatiopalindate is a palindate, there are no rotatiopalindates after (respectively, before) the previous (respectively, next) palindates mentioned.
Since these palindates are rotatiopalindates, they are in fact also the previous and next rotatiopalindates.
The YYYYMMDDhhmm Time Format
The current time in YYYYMMDDhhmm format is 2009 01 05 18 59 (note we use 24-hour format).
Even though this is a time, we shall continue to refer to a palindromic time string as a palindate.
The previous (rotatio)palindate was 2002 12 21 20 02.
The next (rotatio)palindate is 2010 01 10 01 02.
The YYYYMMDDhhmmss Time Format
The current time in YYYYMMDDhhmmss format is 2009 01 05 18 59 18.
The previous (rotatio)palindate was 2005 12 22 21 50 02.
The next (rotatio)palindate is 2010 01 11 10 01 02.
Further Remarks
There are still much work to be done in these areas, including, but not limited to, studying reflexipalindates, relaxing the palindromic condition and simply studying rotatiodates, or studying reflexidates, ignoring the year to identify dates and moments of celebration throughout the year, exploring other date/time string representations such as writing the two digit YY, working in other bases, and counting the number of palindates up to now since year 1AD.
Also, the claims on this page has not yet been confirmed.
If the reader shall find errors in this article, please contact the author.
Acknowledgements
The author would like to thank Po-Ling Loh for the discussion, inspiration, and critique regarding palindates.
She is also the one who first used the nomenclature of "rotatiopalindate," when the author came up with the concept.