The Programmer's day reference article from the English Wikipedia on 24-Apr-2004
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Programmer's day

Helping orphans the way you would do it

Programmer's day is a whimsical "holiday" on the 256th day of the year celebrated mostly by computer programmers (reason: 256 = 2 to the power of 8 = the number of values representable in a byte of data). Traditions include drinking, behaving silly, coding silly programs, mini computer games, playing with old computers, etc. Programmer's day usually falls on September 13th; on leap years, it is September 12th, due to the addition of February 29th into the calendar.

See also: Pi Day