Fibonacci Day: History and Significance

OV Digital Desk
4 Min Read
Fibonacci Day

The Fibonacci Terrace at the Science Centre Singapore. The tiles making up the terrace are arranged to form shapes with sides in proportion to Fibonacci number. | Source: Smuconlaw

Fibonacci Day is observed every year on 23 November to honours one of the most influential mathematicians of the Middle Ages – Leonardo Bonacci. Fibonacci numbers are a never-ending sequence starting with 0 and 1 and continuing by adding the previous two numbers. For example, 0,1,1,2,3,5,8,13,21,34…. are part of Fibonacci series. Once the series was discovered, it started showing up everywhere. Nature is full of Fibonacci patterns, from DNA to hurricanes. It is perceived as “nature’s secret code.”

The Fibonacci numbers are closely related to the Golden ratio and the Golden spiral, the latter of which explains the sequence in a shape form that is often found in nature.

Why do we celebrate Fibonacci Day on 23 November?

We celebrate Fibonacci Day on November 23 because when written out numerically, the date reads the first four digits of the Fibonacci sequence. No matter which day of the week the date falls on, the MM/DD format always reads as 11/23.  The sequence is same as Fibonacci numbers.


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History of Fibonacci Day

A mathematician of the Middle Ages, Leonardo Bonacci — later known as Fibonacci, “the son of” Bonacci — invented a sequence of numbers that shows up constantly in nature, physics, and design.

He was born in 1170 in Italy in a merchant family. Fibonacci travelled with his father, Guglielmo, as a young boy. He learned about the Hindu–Arabic numeral system. He soon realised the many advantages of the Hindu-Arabic system, which, unlike the Roman numerals used at the time, allowed easy calculation using a place-value system.


Fibonacci popularized the Hindu–Arabic numeral system in the Western world primarily through his composition in 1202 of Liber Abaci (Book of Calculation). He also introduced Europe to the sequence of Fibonacci numbers, which he used as an example in Liber Abaci.

Fibonacci Day celebrates this important mathematician and gives us an opportunity to marvel at the way math pervades everything around us. The Fibonacci sequence can be used to calculate the proportions of countless things on Earth and beyond, such as animals, plants, weather patterns, and even galaxies. Pause to observe your surroundings and you’ll start to notice the familiar spiral all around you.

How to celebrate Fibonacci Day?

There are numerous ways to celebrate the day. We can take the opportunity to celebrate the achievements of Leonardo Bonacci who discovered the series.

The sequence occurs very often in common fruits and vegetables. Such a series is available in artichokes, pineapple, Romanesco, and pomegranate. You may either feast upon and share these fruits and share the pattern as well.


The sequence occurs frequently in the human body, and this can be a fun way to show the numbers in action. Some ideas: The bones in a human finger, the spiral in a human ear, and the Golden Ratio proportions of the human eye.

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