The Golden Spiral is marked each November 23 by mathematicians and other scientists, artists and architects, and philosophers of whimsy.
The explanation is a tad geeky: write out the 11th month, 23rd day, just so: 1-1-2-3. There, you have the first numbers in the Golden Sequence, in which each number is the sum of the two numbers before it.
It’s a mathematical interpretation of a profound marvel found throughout the universe. Look for it in grains of sand, the forms of flowers, seashells and tree branches. In the forms of Sankskrit poetry and compelling Renaissance paintings and, magnificently, in the starry spirals in the night sky. The spiral is also one of the main guides used by photographers in composition.
Recognition of the sequence is ancient. It was cited by anonymous Indian mathematicians, and reportedly used by Pingala in Sanskrit poetry. In recent centuries it’s been known as the Fibonacci Sequence, after the middle-ages mathematician Leonardo of Pisa, Leonardo Fibonacci, who introduced it to Western Europeans.
Wikipedia page for the Fibonacci number: https://en.wikipedia.org/wiki/Fibonacci_number