Formules

Calculatrice de dates

Combien de jours se sont écoulés depuis le 1er janvier ? Choisissez le 1er janvier comme date de début et aujourd’hui comme date de fin pour les compter. Cette calculatrice compte les jours entre deux dates quelconques ou ajoute des jours à une date, années bissextiles comprises.

Résultat

Saisissez les valeurs et appuyez sur Calculer pour voir le résultat.

Formule

days=end−start\text{days} = \text{end} - \text{start}

Dates are counted as whole calendar days, including leap days (the end date is not counted twice).

Comment utiliser cette calculatrice

  1. Choose the mode and pick the dates.
  2. The difference counts from the start date up to (not including) the end date.

Exemples corrigés

Days from 1 January to 25 December 2026

25 December is day 359 of 2026, and 1 January is day 1.

So there are 358 days between them: 51 weeks and 1 day.

Easy: days since 1 January, counted on 1 June 2026

January 31 + February 28 + March 31 + April 30 + May 31 = 151 days.

So on 1 June 2026 it had been 151 days since January 1.

Medium: days since January 1, 2025

From 1 January 2025 to 1 January 2026 is 365 days (2025 isn’t a leap year).

From 1 January to 2 November 2026 is 305 more days, so the total is 670 days.

Hard: across a leap day

2024 is a leap year, so February has 29 days.

January 31 + February 29 = 60 days from 1 January to 1 March.

Erreurs fréquentes

  • Counting both the start and end dates: from 1 January to 2 January is 1 day.
  • Forgetting leap years: years divisible by 4 have 29 February, except century years not divisible by 400.
  • Using 30-day months: real months have 28 to 31 days, so always count the actual calendar.

Questions fréquentes

How many days ago was January 1?

Put 1 January of this year as the start date and today as the end date. On 2 November 2026, for example, January 1 was 305 days ago.

Are leap years handled?

Yes — every date is converted to an exact calendar day count.

Does it count the end date?

No. From Monday to Tuesday is 1 day. Add 1 if you want to include both ends.