Add or Subtract Days
Shift a date by days, weeks, months or years.
Use negative numbers to subtract.
How to use
- 1 Enter a start date.
- 2 Set how many days, weeks, months or years to shift by.
- 3 Use negative numbers to subtract instead of add.
- 4 Copy the resulting date and note its weekday.
About Add or Subtract Days
Add or Subtract Days shifts a starting date forward or backward by any combination of days, weeks, months and years, and tells you both the resulting date and the weekday it falls on.
Enter a positive number to move forward or a negative number to move backward — you can mix several units at once, for example adding one year, two months and ten days in a single step.
This is the everyday maths behind deadlines and reminders.
A 90-day notice period, a payment due 30 days after an invoice, a warranty that runs three years, a follow-up scheduled six weeks out — all of these are just a date plus an offset, but doing the arithmetic in your head across month lengths and leap years invites mistakes.
The tool applies calendar months and years first, clamping to the last valid day so that, say, the 31st of January plus one month lands on the last day of February rather than spilling into March.
Day and week offsets are then applied as fixed counts.
The result is shown as a clean ISO date alongside its weekday, with a copy button so you can paste it straight into a calendar or document.
All of it runs locally in your browser, with no accounts or uploads, and the same inputs always produce the same date.
FAQ
How do I subtract instead of add?
Enter a negative number in any field, for example -30 days to move thirty days into the past.
What happens at the end of a short month?
Adding months clamps to the last valid day, so 31 January plus one month becomes 28 (or 29) February rather than overflowing into March.
Can I combine units?
Yes. You can shift by years, months, weeks and days at the same time; calendar units are applied first, then the fixed day and week offsets.