A so-called calendrical savant (or calendar savant) is someone who despite their intellectual disability (typically autism) can name the day of the week of a given date, or visa versa in a few seconds or even a tenth of a second (Kennedy & Squire, 2007).While extremely impressive to behold, calendar calculations are actually very simple to perform and can be learned in less than 30 minutes. This short article will teach you how.

What day was the 13th of January 1989?

My birthday. I was born two weeks late. Here is how to calculate which day of the week that was (Lancaster, 2005):

Step 1. Calculate the Year Code Y

The first step of our five step process is to calculate the year code, represented by the letter Y. This is done in the following way: So, for the date 13th of January 1989 we obtain the year code Y =111.

Step 2. Find the Month Code M

The second step of our five step calculation is to find the month code M. This is a simple step, simply look it up in the table below (or better, memorize it): As we know, leap years occur every four years (even years). Century years like 1900, 2000 and 2100 are leap years if they are evenly divisible by 400.

For the date 13th of January 1989, we obtain the month code M = 1.

Step 3. Find the Day Code D

The third step of our five step calculation is to find the day code D. This iS even easier than finding the month code, as it is simply the number of the date itself. For the 13th of January 1989, the number is D = 13.

Step 4. Find the sum of the numbers Y + M + D

The fourth step of our five step model is to add the three numbers we』ve found. For our three numbers, the sum is 111 + 1 + 13 = 125.

Step 5. Find the Day of the week

The final step of the calculation is to calculate the remainder of the modulo operation 125 mod 7. We know that 7 x 17 is 119, leaving a remainder of 6: The 13th of January 1989 was a Friday. Yes, I was born on Friday the 13th.