23 November - Fibonacci Day/ 23 ਨਵੰਬਰ ਫਿਬੋਨਾਚੀ ਦਿਵਸ
November 23 is celebrated as Fibonacci day because when the date is written in the mm/dd format (11/23), the digits in the date form a Fibonacci sequence: 1,1,2,3
Fibonacci sequence is a series of numbers where a number is the sum of the two numbers before it.
The day honours Leonardo of Pisa (commonly known as Fibonacci), an Italian mathematician who popularised the sequence in his book Liber Abaci (1202).