One date this week has two designations.  10/23/13 is a Minus subtract day because 10 – 23 = Minus 13.

10/23/13 is also Mole day.  From the site www.moleday.org :

Celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m., Mole Day commemorates Avogadro’s Number (6.02 x 10²³), which is a basic measuring unit in chemistry. Mole Day was created as a way to foster interest in chemistry. Schools throughout the United States and around the world celebrate Mole Day with various activities related to chemistry and/or moles.

For a given molecule, one mole is a mass (in grams) whose number is equal to the atomic mass of the molecule. For example, the water molecule has an atomic mass of 18, therefore one mole of water weighs 18 grams. An atom of neon has an atomic mass of 20, therefore one mole of neon weighs 20 grams. In general, one mole of any substance contains Avogadro’s Number of molecules or atoms of that substance. This relationship was first discovered by Amadeo Avogadro (1776-1858) and he received credit for this after his death.

If you are vexed about the paucity of wonderful number dates recently, wait until November. Primes and a sequence await. 

For the coming week, there is one cool date, 10/16/13 is a halfback day.  Go up 6 from 10 to 16, and come half-way back (3) from 16 to 13.  Last week’s monologue on the end of half-back days neglected to remind the meaning of half back days… it is named after the retirees who move from Pennsylvania, New York or Michigan down to Florida and then move half way back to Tennessee or North Carolina when they find Florida is too hot.

Even worse than only one cool date each week in September is this first week in October – NONE!

We will take the opportunity to further explain when Half-BacK Days will end this century. 

Back on 8/25 we discovered that each month has its own curtain call.  For January, 1/31/16 and for February, 2/28/15.

The several formulae being used:

                d = 2y – m   OR   d + m= 2y (see 6/23/13)

There are limits on year, month, and day values:

                0 <= y <= 99  (only 100 years in a century!)

                1 <= m <= 12  (only 12 months in a year!)

                And day limits vary by month

                1 <= d <= 28 or 29 for February

                1 <= d <=30 for April, June, September, and November

                1 <= d <= 31 for January, March, May, July, August, October, and December

 To solve, pick a month and the appropriate day limit.

For March, d = 2y – m <= 31

                Or  2y – 3 <= 31

                Or  2y  <= 34

                Or y <= 17…  3/31/17  up 28 and back 14!

 March:                 3/31/17

April:                     4/30/17

May:                      5/31/18

June:                     6/30/18

July:                       7/31/19

August:                  8/30/19

September:          9/29/19

October:              10/30/20

November:         11/29/20

December:         12/30/21

So we can bid adieu to halfback days at the end of 2021!

September only had one cool date per week.  Even worse, the only cool date from the last week in September is 10/3/13 – an October date!  Addition day (10 + 3 = 13).

 

No one is quite sure why 9/22/13 (22 – 9 = 13) is called a Minus Subtract day, except that the equation is not in the same left-to-right order as the date… but it is cool, nevertheless.

The ONE cool date for this week is a half-back day: 9/17/13.  Go up 8 from 9 to get to 17, then come half way back (4) to get from 17 to 13.  See additional half-back information in the posts on 6/23/13 and  8/25/13, and look for even more on 10/6/13.

Our 2004 silver Honda Pilot reached 110,000 miles on August 31, and 111,111 on September 4.  In between, 111098 (11 10 9 8) went by unnoticed, but I was ready for 111213 (11 12 13) on September 9.

I try to keep a record of where the vehicle was each time a thousand mile mark passes, so I will be watching for 112000 and 113000.  And this year, if I drive few enough miles, I might be able to show the date on the odometer!  I could park the car for two months and drive just enough miles to reach 111513 (11/15/13) on November 15.

As I write this, It’s too late for any date prior to November 12 (11 12 13), and I usually drive about a thousand miles each month, making it unlikely to eke out 113013 on November 30.  But I will watch and hope. 

It will also be a low mileage feat to match the date next year; the first possible opportunity would be 120114, for December 1, 2014.  If somehow I hit that day, then I would just have to drive 100 miles each day thereafter to show the date on the odometer for the whole month (120114, 120214, 120314, …, 123114).  That would be very cool!  After that, the mileage runs out of months, and I don’t want to switch to a European Day / Month / Year display.

For anyone with a brand new car, the first future odometer day you can look for would be 1114, 1/1/14, January 1, 2014.  That’s because any day left in 2013 will have at least five digits (e.g. 9/10/13 is 91013; 10/1/13 is 10113).  In any case, stay alert and check your mileage; there may be a cool odometer number combination just around the corner.  Literally.

Recall that last week had just one cool date.  So it is with EVERY week this month – each week has exactly one cool date.  So, even if there are few total cools, at least they are spaced nicely.

This week, 09/11/13 is a lovely sequence.

Today is Linnea’s birthday and tomorrow is Labor Day, but Thursday is the only cool date this week. 

9 + 4 = 13, so 9/4/13 is an Addition Day!