onlinecalculator.me

Free online add or subtract days calculator

Enter a start date and a number of days, then choose whether to add or subtract. The calculator returns the resulting date and tells you what day of the week it falls on.

Result date
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About this calculator

How to use

  1. Enter your start date.
  2. Type the number of days to add or subtract.
  3. Select “Add days” or “Subtract days”.
  4. Read the result date and day of the week.
  5. Press “Share with my numbers” to copy a shareable link.

How the calculation works

The calculator shifts the start date by the number of whole calendar days you enter. Adding 30 days to April 1 gives May 1; subtracting 30 days from April 1 gives March 2 (or March 1 in a leap year). Every calendar day is counted — weekends and holidays are not skipped.

Worked example

Start date: March 15, 2025. Add 45 days.

  • March has 31 days, so 16 remaining days in March after the 15th.
  • 45 − 16 = 29 days into April.
  • April has 30 days, so 29 days in takes us to April 29.
  • April 29, 2025 is a Tuesday.

Notes

  • The calculator uses local calendar arithmetic — no server calls.
  • Leap years (February 29) are handled automatically.
  • Results represent calendar days, not business days. Use the Business Days Calculator for weekday-only counts.

Frequently asked

How does the calculator add or subtract days?
It shifts the start date by the exact number of calendar days you enter, including weekends and public holidays. No days are skipped — every calendar day counts.
Does it account for leap years?
Yes. The underlying date arithmetic handles February 29 correctly when adding or subtracting across a leap year boundary.
Can I use dates far in the past or future?
Yes. The calculator works for any valid Gregorian calendar date. Results for very distant dates (before 1000 CE or after 9999 CE) may vary by browser.
What does the day-of-week result mean?
It shows the full weekday name (e.g. Tuesday) for the result date, so you can immediately tell whether it falls on a weekend or a workday.
How do I share a link with my date and number pre-filled?
Press "Share with my numbers" to copy a URL that encodes your start date, day count, and operation. Anyone opening that link will see the same inputs.