(Cleared/Gopa)

Madurai: M Jeyachandran, 54, a retired banker and mathematics enthusiast from Tuticorin, can name the day of a week in seconds when given a date in a 10,000 year calendar — from 1AD to 10,000 AD. He exhibited his talent at a record attempt at a private school in Kovur, Chennai, on August 24 and has now officially entered the India Book of Records.

Here is how his formula works. Jeyachandran has given a code value to all the seven days of the week and 12 months of the year ranging from 0 to 6 (see graphic). To know the exact day of a particular date between 1901 and 2099, divide the year in the date by 4. Add the answer (ignore the decimals) to the year, date and the code value of the month. Divide the result by 7 manually. The balance (0 to 6) that cannot be divided by 7 matches the code value of one of the 7 days.

However, Jeyachandran said that this formula works only for dates between 1901 and 2099. “There is a different formula that at times varies from one century to the other,” he said and added that the way it is calculated differs for dates before September 1752 and after September 1752 – as the days from September 3 to 13 were scrapped in the English calendar. There is also a change in the way the day is calculated in a leap year.

“At the record attempt in Chennai, I was given 50 random dates that I answered in less than 5 seconds,” said the man who hails from Maikan Nadar Kudiyiruppu, a village near Tiruchendur in Tuticorin district. He credits the strong foundation he had in mathematics at the Hindu middle school near their village for his finding. “The school gave importance for mathematics,” he said.

After topping the class X board exams and completing plus-two, Jeyachandran enrolled for BCom and later MCom before joining a leading private sector bank headquartered in Tuticorin. After serving the bank for 32 years he resigned as chief manager last year as he could not sit and work for long hours after a road accident. “Now I give maths lectures and also handle a mathematics foundation course at a charted accountancy training institute,” he said.

It was after joining the bank that he started working on more mathematical formulas including the one to find the day, a host of fun and practically useful formulas, derivatives and shortcuts for students, banks and traders. About the day calculation formula, he said that he came out with a basic formula in 1988 and he needed a pen and paper to do it. “I improvised it over the last five years and can give the answer now instantly,” he added.

(Input for graphics)

How it works

Value of the day – Thursday (0), Friday (1), Saturday (2), Sunday (3), Monday (4), Tuesday (5) and Wednesday (6)

Value of the month* – January (1), February (4), March (4), April (0), May (2), June (5), July (0), August (3), September (6), October (1), November (4) and December (6).

Formula – Divide any year between from 1901 to 2099 by 4. Add the whole number arrived with the year, date and the code value given for the month. Divide the number by 7 manually and the remaining number (0 to 6) that cannot be divided by 7 is the exact day.

Example

October 7, 2019

Divide 2019 by 4 = 504 (after ignoring the leftover decimal number 0.75)

Add 504+2019(year) +7(date) +1(code value for October) = 2,531

2,527 is the nearest whole number to 2,531 to be divisible by 7

The remaining whole number is 4 – Value of Monday

October 7, 2019 is a Monday.

(*For a leap year the value of January and February is 0 and 3, respectively. The above mentioned formula only works for the years 1901 to 2099)

Madurai: M Jeyachandran, 54, a retired banker and mathematics enthusiast from Tuticorin, can name the day of a week in seconds when given a date in a 10,000 year calendar — from 1AD to 10,000 AD. He exhibited his talent at a record attempt at a private school in Kovur, Chennai, on August 24 and has now officially entered the India Book of Records.

Here is how his formula works. Jeyachandran has given a code value to all the seven days of the week and 12 months of the year ranging from 0 to 6 (see graphic). To know the exact day of a particular date between 1901 and 2099, divide the year in the date by 4. Add the answer (ignore the decimals) to the year, date and the code value of the month. Divide the result by 7 manually. The balance (0 to 6) that cannot be divided by 7 matches the code value of one of the 7 days.

However, Jeyachandran said that this formula works only for dates between 1901 and 2099. “There is a different formula that at times varies from one century to the other,” he said and added that the way it is calculated differs for dates before September 1752 and after September 1752 – as the days from September 3 to 13 were scrapped in the English calendar. There is also a change in the way the day is calculated in a leap year.

“At the record attempt in Chennai, I was given 50 random dates that I answered in less than 5 seconds,” said the man who hails from Maikan Nadar Kudiyiruppu, a village near Tiruchendur in Tuticorin district. He credits the strong foundation he had in mathematics at the Hindu middle school near their village for his finding. “The school gave importance for mathematics,” he said.

After topping the class X board exams and completing plus-two, Jeyachandran enrolled for BCom and later MCom before joining a leading private sector bank headquartered in Tuticorin. After serving the bank for 32 years he resigned as chief manager last year as he could not sit and work for long hours after a road accident. “Now I give maths lectures and also handle a mathematics foundation course at a charted accountancy training institute,” he said.

It was after joining the bank that he started working on more mathematical formulas including the one to find the day, a host of fun and practically useful formulas, derivatives and shortcuts for students, banks and traders. About the day calculation formula, he said that he came out with a basic formula in 1988 and he needed a pen and paper to do it. “I improvised it over the last five years and can give the answer now instantly,” he added.

(Input for graphics)

How it works

Value of the day – Thursday (0), Friday (1), Saturday (2), Sunday (3), Monday (4), Tuesday (5) and Wednesday (6)

Value of the month* – January (1), February (4), March (4), April (0), May (2), June (5), July (0), August (3), September (6), October (1), November (4) and December (6).

Formula – Divide any year between from 1901 to 2099 by 4. Add the whole number arrived with the year, date and the code value given for the month. Divide the number by 7 manually and the remaining number (0 to 6) that cannot be divided by 7 is the exact day.

Example

October 7, 2019

Divide 2019 by 4 = 504 (after ignoring the leftover decimal number 0.75)

Add 504+2019(year) +7(date) +1(code value for October) = 2,531

2,527 is the nearest whole number to 2,531 to be divisible by 7

The remaining whole number is 4 – Value of Monday

October 7, 2019 is a Monday.

(*For a leap year the value of January and February is 0 and 3, respectively. The above mentioned formula only works for the years 1901 to 2099)

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