La Wikipedia indica que el día 256 del año, es día del programador.
Programmer’s day is a ‘holiday’ on the 256th day of the year celebrated mostly by computer programmers. The date is significant to programmers because 256 = 2 to the power of 8 = the number of values representable in a byte of data.
Traditions include behaving in silly ways, editing Wikipedia, playing Demo Ball, coding silly programs, mini computer games, playing with old computers, etc. That, of course, includes the condition that the developer who chooses to celebrate, needs to have done decent coding on all the other days and had tried the best not to be silly on the other days. For those programmers who are used to the ‘celebrations’ in their every day lives, this ‘holiday’ becomes unjustified. Programmer’s Day usually falls on September 13th; on leap years, it is September 12th.
Some people feel that counting should start from 0. However, even counting from 0 does not change the fact that there are still only 256 values that can be represented in a byte. Therefore, if counting starts at zero, then the 256th day falls on the number 255 which does not change the day that the holiday falls on.