How many friday the 13th in a year?
Mathematica 49 46 45 44 42
As a pure function: 42 chars
DayName@{#,m,6}~Table~{m,12}~Count~Friday&amp;

Example
DayName@{#,m,6}~Table~{m,12}~Count~Friday&amp;[2013]


2


As a named function: 44 chars
f=DayName@{#,m,6}~Table~{m,12}~Count~Friday&amp;

Examples
f[1776]
f[2012]
f[2013]
f[2014]


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