Odd Day

Somewhere along the line, perhaps during the years when I worked with many Europeans at Pfizer, I began writing dates as DD-MM-YYYY. When you think about it, this really makes sense, going from the particular (day) to the next level (month) to the highest level (year).

Here in the US, dates are usually written as MM-DD-YYYY. Hence the date today is 11-13-15, which consists of three consecutive odd numbers. That raises a question: how often does it occur that the date can be written as three consecutive odd numbers?

Every year has a maximum of 12 months, each month a maximum of 31 days, and each century consists of 100 years.

The odd months in each year are 1, 3, 5, 7, 9, 11

The odd days in each month are 1, 3, 5, 7, 9, …, 31

The odd years for each century are 1, 3, 5, 7, 9, 11, 13, 15,……99

So, we have six days in each century that follow the pattern:

1-3-5

3-5-7

5-7-9

7-9-11

9-11-13

11-13-15

In other words, this configuration will not appear again until the 22^nd Century, January 3^rd of 2105 (1-3-5) to be precise!

Just to have some fun, how does this work for even numbers?

The even months in each year are 2, 4, 6, 8, 10, 12

The even days in each month are 2, 4, 6, 8, …, 30

The even years for each century are 2, 4, 6, 8, 10, 12, …

So we have

2-4-6

4-6-8

6-8-10

8-10-12

10-12-14

12-14-16

If I have gotten this correctly, December 14^th of next year is the very last time this can happen until we get to the 22^nd century, right? Barry just told me he does not expect us to be around to see it on January 3^rd of (210)5, so we should enjoy it now.

I am getting dizzy just thinking about this.

Thanks to my sister Wendy for sharing this with me.

Have a nice weekend,

Love,

Rebecca