Programmers' Day is an international professional day recognized in many technology companies and programming firms, that is celebrated on the 256th (hexadecimal 100th, or the 28th) day of each year (September 13 during common years and on September 12 in leap years). It is officially recognized in Russia[1][2] and observed in several other countries, including Argentina, Australia, Austria, Bangladesh, Belarus, Belgium, Brazil, Bulgaria, Canada, Chile, China, Croatia, Czech Republic, Denmark, Estonia, France, Germany, Guatemala, India, Ireland, Israel, Italy, Latvia, Mexico, Mongolia, New Zealand, Palestine, Pakistan, Papua New Guinea (highland region), Poland, Romania, Serbia, Slovakia, Slovenia, South Africa, Ukraine, the United Kingdom, the United States and Uruguay.[citation needed]

The number 256 (28) was chosen because it is the number of distinct values that can be represented with an eight-bit byte, a value well-known to programmers.[3] 256 is also the highest power of two that is less than 365, the number of days in a common year.

Link ~> http://en.wikipedia.org/wiki/Programmers'_Day