# Is it possible for Good Friday to fall on the 13th?

Source: http://mathforum.org/library/drmath/view/52364.html
From: Susan Melanson
Subject: Good Friday on the Thirteenth

How many times has Good Friday fallen on the 13th? I have looked at
your formulas and don’t seem to find one that fits this question,
since Good Friday doesn’t fall on the same date each year. I’ve looked
at some other sources as well, to no avail.

Thanks for your help on this,
Susan Melanson

Check out the above website for the answer! It turns out that Good Friday will fall on the 13th approximately once in 29 years.

Wishing all Christians a blessed Good Friday. Also check out this Wikipedia page on how to calculate the date of Easter (http://en.wikipedia.org/wiki/Date_of_Easter)

The calculation of the date of Easter is called Computus. It turns out calculating the date of Easter is quite complicated. Even the great Mathematician Gauss made a mistake (see http://en.wikipedia.org/wiki/Date_of_Easter#Gauss_algorithm).

In 1800, the mathematician Carl Friedrich Gauss presented this algorithm for calculating the date of the Julian or Gregorian Easter and made corrections to one of the steps in 1816. In 1800 he incorrectly stated p = floor (k/3). In 1807 he replaced the condition (11M + 11) mod 30 < 19 with the simpler a > 10. In 1811 he limited his algorithm to the 18th and 19th centuries only, and stated that 26 April is always replaced with 19 April and 25 April by 18 April. In 1816 he thanked his student Peter Paul Tittel for pointing out that p was wrong in 1800.

## Carl Friedrich Gauss

Johann Carl Friedrich Gauss (/ɡs/; German: Gauß, pronounced [ɡaʊs] ( listen); Latin: Carolus Fridericus Gauss) (30 April 1777 – 23 February 1855) was a German mathematician and physical scientist who contributed significantly to many fields, including number theory, algebra, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics.

Sometimes referred to as the Princeps mathematicorum (Latin, “the Prince of Mathematicians” or “the foremost of mathematicians”) and “greatest mathematician since antiquity“, Gauss had a remarkable influence in many fields of mathematics and science and is ranked as one of history’s most influential mathematicians.  