Programmers' Day is celebrated worldwide on the 256th day of the year, which falls on September 13 during common years and September 12 during leap years. The holiday was first proposed by Russian programmers Mikhail Chervyakov and Valentine Balt, who selected the number 256 because it represents the distinct values of a byte, consisting of eight bits. Initially celebrated in 2002, it gained international recognition through the Internet, with an official decree by Russian President Dmitry Medvedev in 2009 establishing it as a professional holiday in Russia. While September 12/13 is the primary observance, some programmers also celebrate on January 7, December 10 (Ada Lovelace's birthday), and April 4 (Saint Isidor of Seville's feast day). The day honors the contributions of programmers and the importance of their work in technology.