It is the day of the year that follows the beginning of the Fibonacci number sequence. 1, 1, 2, 3, and so on. Each subsequent number is the total of the two previous.
Though it originally appeared in Indian mathematics, in Sanskrit, Leonardo of Pisa (known as Fibonacci) wrote about it in his book Liber Abaci in 1202.
The graphic above shows the sequence. It is used in computer programs and has many other applications.
But the one thing that draws me to Fibonacci is the way you can find it in nature. You can see the sequence in everything from flower petals to fruits and vegetables and my favorite, the shell of the Nautilus.
I usually stink at math but in this case I find it to be quite beautiful. Poetic, even.
If you want to learn more about Fibonacci numbers and their applications here is a great website that explains it all.
I hope you enjoy your Fibonacci Day!