Boneyard Tools

Add or Subtract From a Date

Pick a start date, then add or subtract any mix of days, weeks, months and years. Use negative numbers to go back in time. Month-end and leap days are handled correctly.

How to add to or subtract from a date

  1. Choose your start date.
  2. Enter how many days, weeks, months or years to add (use negatives to subtract).
  3. Read the resulting date and copy it.

Examples

Add 30 days

2026-06-10 + 30 days
2026-07-10

Month-end overflow

2026-01-31 + 1 month
2026-02-28

Frequently asked questions

How do I subtract instead of add?

Enter a negative number in any field. For example -7 days moves the date one week earlier.

What happens with Jan 31 plus one month?

Because February has no 31st, the result clamps to the last day of February, giving February 28 (or 29 in a leap year).

In what order are the units applied?

Years and months are applied first on the calendar, clamping the day if needed, then weeks and days are added as exact day offsets.

Does daylight saving time affect the result?

No. Dates are computed in UTC, so the answer is always a clean calendar date with no time-zone drift.

Is my data private?

Yes. The calculation runs in your browser and nothing is uploaded.

Related tools