Date Add & Subtract Calculator
Add or subtract years, months, weeks and days from a date. Results update as you type.
Enter your details
Results
Fill in the details above and the results appear here.
About the Date Add & Subtract Calculator
Add or subtract years, months, weeks and days from any date to find a deadline, a due date, a notice-period end or a warranty expiry. Leave the start date blank to count from today.
The result shows the weekday, the day of the year and the ISO date format.
The calculation runs in your browser, so the numbers you enter are not uploaded or stored.
Date Add & Subtract Calculator example
Start date: 2026-01-31
Years: 0
Months: 1
Weeks: 2
Days: 5Date after adding: Thursday, 19 March 2026
ISO date: 2026-03-19
Day of the year: 78
Calendar days apart: 47
Start date was a: SaturdayHow it is calculated
Years and months are applied first. If the target month is shorter than the start day, the result moves to the last day of that month, so 31 January plus one month is 28 February (29 in leap years). Weeks and days are then added exactly.
Years and months are added first (to the same day of the month, or the last day if it is shorter)Weeks × 7 and days are added after thatDay of year counts 1 January as day 1
How to use the Date Add & Subtract Calculator
- Fill in the fields above. Required fields are marked, optional ones can be left blank and fall back to the defaults described on this page.
- Use “Try an example” to see a worked case, then replace the numbers with your own.
- Read the results as you type. The large card is the main answer and the smaller cards are the related figures.
- Copy a single value or everything, or share a link that keeps your inputs.
Date Add & Subtract Calculator FAQ
How does the date add & subtract calculator work?
Years and months are applied first. If the target month is shorter than the start day, the result moves to the last day of that month, so 31 January plus one month is 28 February (29 in leap years). Weeks and days are then added exactly.
What is 31 January plus one month?
It is the last day of February: 28 February, or 29 February in a leap year. Calendar months have different lengths, so the calculator never skips into March.
Can I add and subtract at the same time?
No, one operation at a time. To go forward and back, run it twice or enter the net number of days.
Is this date add & subtract calculator free and private?
Yes. It is free with no sign-up, and the calculation happens on your device, so your numbers are never sent to a server.
More personal life calculators
Working Days CalculatorRetirement Age CalculatorDays Until an Event CalculatorSleep Cycle CalculatorBirthday Countdown Calculator
All personal life calculators → · All everyday calculators →