Saturday, January 29, 2022

How 823 Years Shrunk to One ...

 I happened to read a WhatsApp message:

“[T]his year’s February has the following that happens only once in 823 years. This coming February has: 4 Saturdays, 4 Sundays, 4 Mondays, 4 Tuesdays, 4 Wednesdays, 4 Thursdays, 4 Fridays.”

To start mildly, the above must have originated from an Indian citizen; others usually do not use, while referring to the future, “coming”, or other adjectives like, “going”, “walking” running”, “triple jumping” etc.! “[C]oming” gives it away – Indian English in WhatsApp!

Also, I would speculate, that the person who started off this must have done it as a joke, to catch his fandom by surprise. He should have been hoping to make a few of them the butt of his joke.

What is so special about 823? I took a wild guess and checked whether it is a prime number. Google told me, yes, it is!

Prime numbers are the prime suspects in such, “... won’t repeat in so many days/years/centuries” etc. in calendrical matters. The reason could be that it gives you a number that is far away in the future that one has to be motivated enough to do a bit of digging (in her Google calendar). The next step is to check the calendar for the year 2845 CE, and see whether it is a Leap Year or not. We learnt that any year divisible by four, except for end-of-century years for which the controlling divisor is 400, is a Leap Year, February carrying 29 days.

2845 is not divisible by four to give an integer quotient (if one merely says it is not divisible by four, one can always respond, “No, it is divisible and the quotient is 711, and the remainder, one). Hence, it is not a Leap Year.

 So, the moment Google spit out the calendar for 2845 CE and confirmed that it is not a Leap Year, everything became clear to me – why the originator of the factotum sent that out – to make a fool of those who fall for WhatsApp!

The simplicity of the explanation is stunning – 2845 CE (2022+823) is NOT a Leap Year and therefore it has only 28 days – easily divisible by seven, the number of days in a week.

Voila!  Each weekday repeats only three times in February, 2845! You would have four of Saturday and also each of the other days!

But, the whole exercise is much simpler (and hence I reserved it for the last): The next year would have only four of each day of the week in February!

So, the heading of this post is crystal clear, at least to me: We do not need to wait till 2845 CE. 2023 CE will do equally fine!

The teaching moment: If you wanted to fool someone, go to WhatsApp! Here, as I noted, only one person so far has revealed that he is a fool.

Raghuram Ekambaram

 

2 comments:

N. Subramanian said...

I simply delete such messages!

mandakolathur said...

Yes, Mr. Subramanian, that is what Alexander of Macedonia did! But, that way, you do not get material for one blog post :).

Seriously, I just lament the unthinking crowd behavior. Oen may say that I am stupid to expect reasonable thinking on the part of a crowd...

Raghuram Ekambaram