When is the ideal date for Programmer's Day?

September the 13th is celebrated in some quarters as Programmer's Day. In fact, Engadget published an article to commemorate the event.

However, the reason that the 256th day of the year, i.e. the 13th of September, is assigned as the Day of the Programmer, in my opinion, does not have a relevant enough inspiration. The number 2 raised to the power 8, i.e. 256, was chosen since 8 bits constitute one byte (The fundamental unit of Computer Memory).

But does the byte truly represent the spirit of programming? It's a data-type, and yes, at the lower end of the hardware coding spectrum, it does seem to represent a significant block, but Programmer's Day is about commemorating the spirit of programming that has made everything from computers a reality.

My recommended date for Programmer's Day is the 28th of December, the birthday of John von Neumann, the man behind the stored program concept. The concept simply states that instructions can be stored for systems to retrieve and run subsequently. This, I believe, is the very foundation for programming as we know it.

There are other several great occasions littered in the history of computing, with personalities who redefined and revolutionized the limits the computing. When, in your opinion, is the ideal date for commemorating Programmer's Day?