A small math experimentPi Cumple Vercel App: Find your birthday in π
Pi Cumple turns a date into a search for digits of π. Open the Spanish browser app at pi-cumple.vercel.app, enter a day, month and year, and watch a strip of digits settle on the matching sequence. Start with a sample date and compare its full result with its shorter day-and-month match.
Open Pi Cumple ↗
Why it’s here
This is a small math experiment you can finish in one sitting. Both results use the same date, so you can change the length of the search string without changing its first four digits. Try 14 March 2000 and compare where 14032000 and 1403 first occur. The shorter sequence is a prefix of the longer one, so it can occur at the same position or earlier.
How to read the two results
The big number is the position of the highlighted string, counting the first decimal after 3 as position 1. The sentence below describes how many digits come before it. Read the highlighted characters as well as the number: eight digits mean the full date matched, while four mean you are seeing the day-and-month lookup.
Make it a two-date experiment
Keep the day and month fixed and change the year. The full eight-digit string changes, but the four-digit string stays the same. For example, changing the year from 2000 to 2001 moves the full-date result from 121,817,702 to 4,685,715. The shorter 1403 result stays at 6,053. A classroom or family can use sample dates and compare outcomes without entering anyone’s birthday.
When the year drops out
The app covers full dates from 1900 through 2030. An out-of-range year produces a day-and-month result. The app also identifies two dates inside the range that have no full match in its search window: 18 September 1947 and 28 June 1971. It still shows the shorter sequence, so check the label before copying the result.
How to search for a birthday in π
- Open Pi Cumple and fill Día, Mes and Año in that order.
- Use 14, 03 and 2000 to look up the sample date.
- Select Buscar en pi and read the highlighted eight-digit string.
- Compare the main position with the Solo día y mes line. Change only the year to see which number changes.
Pi Cumple screenshots
The original Spanish interface, captured on November 10, 2026 using sample dates.
Pi Cumple frequently asked questions
What is the Pi Cumple Vercel app?
It is a Spanish browser tool that looks for a calendar date in the first billion decimal digits of π.
What format does Pi Cumple use?
The full date uses DDMMYYYY, with leading zeros for single-digit days and months. For example, 4 May 2001 becomes 04052001.
What is the first decimal position?
The first digit after the decimal point in 3.14159… is 1, at position 1. The number 3 is before the decimal point.
Why did I get only four highlighted digits?
The app shows DDMM when the year is outside 1900–2030 or the full date is missing from its search window.
Can I try it without entering my real birthday?
Yes. Use any valid sample date, such as 14 March 2000. The app searches the digits formed from the date you enter.
Is the original app available in English?
The original interface we reviewed is in Spanish. NavSprout provides this guide in English and Spanish.
Does a missing date mean it never appears in pi?
The lookup covers a finite prefix of one billion decimals. A missing match only describes that prefix.
Source and review
We tested a full match, a four-digit fallback and invalid-date validation in the browser. The app attributes its digit source to MIT and credits the channel «¿Qué más crees que hace…?».