Fibonacci Day
Fibonacci Day on 23 November, written 11/23 in the US, celebrates the number sequence 1, 1, 2, 3 and its patterns in nature.
- UK (not marked)
- USA
- Ireland (not marked)
- Canada (not marked)
- Australia (not marked)
- New Zealand (not marked)
- UAE and Gulf (not marked)
- International (not marked)
About the day
Fibonacci Day falls on 23 November because the date written in the US style, 11/23, matches the start of the Fibonacci sequence: 1, 1, 2, 3. Each number in the sequence is the sum of the two before it. Leonardo of Pisa, known as Fibonacci, introduced it to Europe in his 1202 book Liber Abaci, along with the Hindu-Arabic numerals in use today. The related golden ratio appears in flower petals, seashells, hurricanes and spiral galaxies.
People mark the day by reciting the sequence as far as they can, looking for the golden ratio around them and drawing, sculpting or baking Fibonacci spirals. Posts use #FibonacciDay.
The day suits schools, maths and science educators, museums, edtech firms, design studios and science media.
Dates for the next three years
| Year | Date | Where | Status |
|---|---|---|---|
| 2026 | Monday 23 November 2026 | USA | Same date every year |
| 2027 | Tuesday 23 November 2027 | USA | Same date every year |
| 2028 | Thursday 23 November 2028 | USA | Same date every year |
Sectors this day suits
Types of business that could link their activity to this day.
- Schools
- Maths educators
- Science museums
- Edtech
- Design studios
- Science media
Questions and answers
When is Fibonacci Day 2026?
Fibonacci Day 2026 is on Monday 23 November 2026. It falls on the same date every year.
Who organises Fibonacci Day?
Fibonacci Day has no single organiser. Many organisations mark it independently.
Where is Fibonacci Day marked?
Fibonacci Day is marked in the USA.
Where do these details come from?
We checked these details against one source, including National Today: Fibonacci Day. They were last checked on 7 November 2026.
Where this information comes from
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