Tag Archives: Everyday Math

Month, Day, Year: A Number Sequence

Month, Day, Year: A Number Sequence

Daily journaling is one of the constants in my life. Over many years, I don’t believe there has been a single day when I did not make at least half a dozen entries in my journal. Each entry is dated, so on any given day I will write the date at least half a dozen times. Already today I have written 2/4/13 eight times. I’m not sure exactly when, but somewhere in 2004 or 2005 I started to pay attention to the numbers in this month, day, year sequence of whole numbers. I soon realized that something kind of interesting was happening during these early years of this century.

As I started to pay attention it dawned on me that there would be exactly one day in each year when the numbers in this month, day, year sequence will be consecutive whole numbers. From that point on I started to anticipate that day. I remember just a few months ago when every date in my journal was 10/11/12 and while I was excited about it, I understood and was disappointed to think that it would be more than a year before the date in my journal would again be a sequence of consecutive whole numbers.


Actually, what is even more disappointing is that there are only a couple of more years in this century when this sequence will occur. The last time will, of course, be in December of 2014 when I will be able to write 12/13/14. Probably for most of us that will be the last chance we will have in our lifetimes.

Reflecting back, I understand that the first opportunity for such a sequence in my lifetime was in January of 2003 when the date would have been 1/2/03. There are just twelve years in any century when this is possible. I consider myself fortunate to have noticed this pattern early enough in the century so that I have had the pleasure of being aware of writing these special dates at least seven or eight times, and there are yet two more coming up.

Of course, there are other dates for which this sequence of numbers is just as interesting. For example, another one to which I’ve paid attention is when all three numbers are the same. That happened for the last time in this century on 12/12/12.

As I’ve been writing this post, other possible sequences have come to mind and now I wish I’d been watching for them as well. For example, 3/4/05 is not only a sequence of consecutive whole numbers, but it is also a Pythagorean triple. Notice that 3 squared plus 4 squared is equal to 5 squared. What would be another such month, day, year sequence where the sum of the squares of the first two numbers is equal to the square of the third number? I can think of at least five more. Or what if the sequence is consecutive odd numbers, or consecutive even numbers, or consecutive prime numbers?

Well, such is the life of one who cares, probably too much, about patterns and sequences of numbers. If you have similar experiences with number sequences that pop up in everyday life, let me hear from you. You can simply leave a comment.