Le guide ci-dessous n'est pas encore disponible en français et s'affiche en anglais. Le calculateur lui-même est entièrement traduit.
Comment utiliser ce calculateur
- Choose a start date (today by default).
- Choose add or subtract.
- Enter any combination of years, months, weeks and days.
Formule
Years and months are applied first, keeping the day of the month where possible. If that day doesn't exist (for example the 31st in a 30-day month), the result uses the last day of the month. Weeks and days are then added as exact numbers of days, so leap years are handled automatically.
Jan 31 + 1 month = Feb 28 (or Feb 29 in a leap year)
Mar 1 − 1 day = Feb 28 or 29
Example
- 8 November 2026 + 90 days = 6 February 2027.
- 31 August 2026 + 6 months = 28 February 2027.
Questions fréquentes
Does the start date count as day 0 or day 1?
The start date is day 0, so adding 1 day gives tomorrow. To count both start and end dates, use the day counter.
How do I count only business days?
Use the business days calculator, which skips weekends and optional holidays.
Why is adding 30 days different from adding 1 month?
Months have 28 to 31 days. Adding a month moves to the same day number in the next month; adding 30 days always moves exactly 30 days.