Programmers' Day (Russian: День программи́ста) is an international professional holiday, recognized in many technology companies and programming firms , that is celebrated on the 256th (0x100th) day of each year (September 13 during common years and on September 12 in leap years). It is also officially recognized in Russia and observed in several other countries including Poland, the United States, United Kingdom, New Zealand, France, China, India, Guatemala, Slovenia and Croatia.
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. Starting from zero, the 256th value represented by a sequential permutation of 8 bits is unsigned integer 255, hexadecimal 0xff or binary 0b11111111. 256 is the highest power of two that is less than 365, the number of days in a common year.Source
Happy coding ))