Programmers' Day 2027 is on Monday

About Programmers' Day

The day is a professional celebration for software developers, coders, testers and everyone else whose job involves writing instructions for computers. It is mostly marked inside tech companies, developer communities and computer science departments, with team lunches, talks, coding challenges and a fair amount of in-jokes about binary numbers.

The date is the joke. A byte is made of eight bits, so it can represent 2 to the power of 8, or 256, different values. The 256th day of the year is also written as 100 in hexadecimal notation, and 256 is the largest power of two that fits inside a calendar year. In common years that day is September 13; in leap years, when February has 29 days, it moves to September 12.

The idea of a programmers' holiday on this date was promoted in Russia as early as 2002, when Valentin Balt, who worked at the Moscow web studio Parallel Technologies, drafted an appeal to the Russian government and began collecting signatures for it, according to a 2007 report in the Moscow newspaper Vechernyaya Moskva. In 2009 the Ministry of Communications and Mass Media put forward a draft order, and on September 11, 2009, President Dmitry Medvedev signed an executive order making the Day of the Programmer an official professional holiday in Russia. The Kremlin's announcement stated that it would fall on the 256th day of each year.

Outside Russia the day has no official status, but it is widely shared among developers worldwide. It is a working day everywhere, including Russia, where professional days honor an occupation rather than give people time off. Some programmers in China informally mark October 24 instead, since 1024 is another power of two.

Sources: Kremlin (archived): Dmitry Medvedev issued an executive order establishing a new professional holiday, Programmers' Day (September 2009), Vechernyaya Moskva (archived, in Russian): Праздник 256-го дня (2007). How we check dates.

How to mark Programmers' Day

• Thank a developer on your team for a specific fix or feature that made your work easier.
• Write or improve the documentation for a tool you maintain, so the next person has an easier time.
• Contribute a small bug fix, test or translation to an open-source project you rely on.
• Teach a friend or a child the basics of a programming language with a short beginner exercise.
• Hold a team retrospective on technical debt and pick one item to clean up this month.
• Read about an early computing pioneer, such as Ada Lovelace or Grace Hopper.

Programmers' Day dates