My birthday this year (2011) is on a Friday. In most years, one’s birthday the following year is on the subsequent day of the week, and in that pattern, my birthday next year (2012) it is on a Saturday. However, due to 2012 being a leap year, my birthday in 2013 will be on Monday […]

I’m not a very smart man. I’m trying to count how many years I’ve been working at my new job. I started in May 2011. If I count the years separately, I get that I’ve worked 4 years – 2011 (year 1), 2012 (year 2), 2013 (year 3), 2014 (year 4). But if I count […]

As previously there were a method to find the date from the year 1893 to 2032 , which is very difficult to take a list of table always . Is there any other easy way to find the day of any date ?

In Summer Wars the main character (he is a mathematician) calculates the day of the week of someone’s birthday (19/07/1992 is Sunday). I know (very) basic modular arithmetic but I can’t figure out how to do it. Can someone point me to the right direction? It seems fun to do.

There are many descriptions of the “birthday problem” on this site — the problem of finding the probability that in a group of $n$ people there will be any (= at least 2) sharing a birthday. I am wondering how to find instead the expected number of people sharing a birthday in a group of […]

Everyone knows Friday the 13th is regarded as a day of bad luck. Why does every year have at least one of this bad day?

Intereting Posts

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For $x\in\mathbb R\setminus\mathbb Q$, the set $\{nx-\lfloor nx\rfloor: n\in \mathbb{N}\}$ is dense on $[0,1)$
How do we know whether certain mathematical theorems are circular?
Analytical Expression to find the Shortest Distance between Two Ellipses?
Proving the Mandelbrot set is bounded
How to use mathematical induction with inequalities?
Continuity of polynomials of two variables
Closed-forms of real parts of special value dilogarithm identities from inverse tangent integral function
Upper bound on the number of charts needed to cover a topological manifold
If $A|B$ and $B|A$ then prove $A=\pm B$
Is there a binary spigot algorithm for log(23) or log(89)?
What is $\Bbb{R}^n$?
$\log_9 71$ or $\log_8 61$
Degree of a function
what is wrong in my proof using simple induction?