Adding or Subtracting Days from a Date
Date arithmetic answers a practical question: what date is N days from here? The tool shifts the calendar directly, lets the month, year and leap day roll over, and reports the weekday of the result.
Open the tool：Date Add / Subtract Calculator
Contracts, warranties and shipping dates
A contract signed today promises completion within 90 calendar days, and you need the last date. 25 October 2026 plus 90 days is 23 January 2027; counting across the year boundary by hand is where mistakes happen. The tool gives the date and weekday, so a weekend landing is visible immediately.
Warranty expiry, return windows, trial periods and payment 30 days after invoice all use the same arithmetic. Getting the start date right matters: a clause that runs from the date of signing usually includes that day, while one that starts the next day shifts everything by one.
- Find a contract expiry or warranty end date
- Project a delivery date N days after dispatch
- Check whether the result lands on a weekend
Calendar days, whole days and leap years
The tool counts calendar days, so Saturdays, Sundays and holidays all count. Only whole days are used: 2.5 is treated as 2. A negative number goes backwards, for example -30, and 0 returns the same date. Dates are entered and returned as YYYY-MM-DD, with the weekday alongside.
Month ends and leap years are handled by the calendar: 31 January plus one day is 1 February, 28 February in a common year becomes 1 March, and in a leap year it becomes 29 February. It never produces 30 February, but it also never rolls forward to a working day on its own.
- Calendar days: weekends and holidays count
- Whole days only; a negative number goes back
- 29 February is handled without overflow
It does not do business days or months
For 90 business days later, this tool is the wrong instrument: count in business days and then overlay holidays. For three months later, adding 90 days is also wrong, because months differ in length and the contract must say how month-end is treated.
The output is a date calculation, not legal advice. Contracts distinguish calendar days, business days and rolling to the next working day, and a dispute is settled by the text and the applicable law. Cross-border work adds a time-zone wrinkle that can move the date by one.
- Business days, months and years need other tools
- Month-end rules belong in the contract
- Cross-border work: watch the time-zone date shift
FAQ
Calendar days or business days?
Calendar days. Weekends and holidays are included, so if the result falls on a Saturday you must roll it forward yourself. If the contract says business days, use the workday counter instead.
Does it handle 29 February?
Yes. The system calendar does the arithmetic, so 29 February plus one day is 1 March, never 30 February. In a common year, 28 February plus one day is also 1 March, and the year increments automatically.
Can it show the gap between two dates?
No. It shifts one date only. For a difference, use the workday counter or a dedicated date-difference tool; to verify a shift, subtract the start date from the result and check the number of days.
Related tool：Date Add / Subtract Calculator