Programmer's Day!

Programmer's Day — a professional holiday of programmers, celebrated on the 256th day of the year (the 255th, counting from zero). The number 256 (2^8) was chosen because it is the number of distinct values that can be expressed with an eight-bit byte. Also, «256» in hexadecimal is «100» («0x100»). And it is also the largest power of 2 that is less than 365 (the number of days in a year).

In a non-leap year the holiday falls on September 13, and in a leap year on September 12.