Add Days to Date Calculator
Pick a start date, then choose how much time to add or subtract to find the new date.
Worked examples
Adding 90 days
Start 15 October 2026 plus 90 days
Wednesday 13 January 2027.
The count moves forward through each month in turn, so the result lands in January.
Adding a month to 31 January
Start 31 January 2026 plus 1 month
28 February 2026.
When the start day does not exist in the target month, the last day of that month is used.
About Add Days to Date Calculator
An add days to date calculator works out the date that comes a set amount of time before or after a start date. You might use it to find a return date for a parcel, the end of a probation period, the day a notice period finishes or the date a warranty runs out. Choose whether to add or subtract, enter the amount, and pick days, weeks, months or years. The result is shown in full with the day of the week, so you can see straight away whether it falls on a weekday or at the weekend.
Months and years need a little care. When the start day does not exist in the target month, the calculator uses the last day of that month. For example, adding one month to 31 January gives 28 February in most years, or 29 February in a leap year. Adding one year to 29 February gives 28 February in the following year. Weeks are always seven days, and days are counted in whole calendar days, so the result is accurate whatever the time of year.
How to use Add Days to Date Calculator
- Pick the start date.
- Choose Add or Subtract.
- Enter a whole number of 0 or more.
- Pick days, weeks, months or years.
- Read the new date and the day of the week it falls on.
Common uses
- Working out when a notice period or probation period ends.
- Finding the return or refund deadline for a purchase.
- Calculating a due date or review date several months ahead.
- Checking when a warranty or contract term runs out.
Frequently asked questions
How do I subtract days from a date?
Choose Subtract in the first box, enter the amount and pick the unit. For example, to find the date 14 days before 1 March 2027, choose Subtract, enter 14 and choose Days. The result is 15 February 2027. Enter the amount as a positive number and pick Add or Subtract, since a minus sign is not needed.
What happens when I add months to the 31st?
If the target month has fewer days than the start date, the result uses the last day of that month. Adding one month to 31 March gives 30 April, and adding one month to 31 January gives 28 February in a common year. This matches how most people expect calendar months to behave, and it avoids dates that do not exist.
Does adding weeks count the same as adding seven days?
Yes. Adding two weeks is exactly the same as adding 14 days. The calculator converts weeks into days, so there are no gaps or overlaps. This is useful for fortnightly payments, two week notice periods, or plans that run in blocks of seven days.
Can I use the result in another calculation?
You can copy the result with the copy button and paste it into a calendar, spreadsheet or email. To go further, use the result as the new start date and add more time. For example, add three months, then add ten days, to reach a date that combines both periods. Always check the final date against the terms of any contract or agreement.
What is the furthest date I can calculate?
The calculator works for results between the years 1000 and 9999. You can enter an amount of up to 100,000 at a time. If the result would fall outside those years, the calculator shows a message instead of a date. For longer spans, split the calculation into several steps, using each result as the next start date.