Born on November 23
Fibonacci Day
One, one, two, three, and onwards.
Next: November 23, 2026
Where it comes from
Fibonacci Day is an informal day with no known founder or organising body. It falls on 23 November because, written month first as 11/23, the date reads 1, 1, 2, 3: the start of the Fibonacci sequence, in which each number is the sum of the two before it.
How it's celebrated
Maths teachers use the day for puzzles, and people share the sequence and its spirals online. Easy ways to join in: continue the sequence as far as you can (5, 8, 13, 21 …), try Fibonacci's rabbit puzzle, or count the spirals on a pine cone or sunflower head, which usually come in neighbouring Fibonacci numbers.
Did you know
Fibonacci learned what he called 'the art of the Indians' nine symbols' as a boy in Bugia, now Béjaïa in Algeria, where his father represented Pisan merchants.
Read the full story of Fibonacci Day
Star sign
Sagittarius · November 22 – December 21 · Fire sign
Restless and optimistic, always planning the next adventure.