How are months and years handled?

Adding months or years shifts the calendar month or year directly. As with calendars generally, the day may roll into the next month when the target month is shorter, for example 31 January plus one month.

Can I count backwards from a date?

Yes — choose "Subtract" to count days, weeks, months or years before the start date, for example to find a deadline that is 30 days earlier.

Does adding 7 days equal adding one week?

Yes. Adding one week shifts the date by exactly 7 calendar days, so "add 1 week" and "add 7 days" always produce the same result.

What happens when I add a month to the 31st?

The tool shifts the calendar month directly. When the target month has fewer days — for example 31 January plus one month — the date rolls forward into the following month, as standard calendar arithmetic does.

Is my date uploaded anywhere?

No — every calculation runs entirely in your browser and nothing is ever uploaded.

What is the Add or Subtract Days Calculator?

Free add or subtract days calculator — add or subtract days, weeks, months or years from any date and see the resulting date and weekday. Runs entirely in your browser, nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Add or Subtract Days Calculator

Name: Add or Subtract Days Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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The Add or Subtract Days calculator shifts any date forward or backward by a number of days, weeks, months or years and shows you the resulting date and its weekday. It answers everyday questions like “what date is 90 days from now”, when a notice period ends, or when a subscription renews — without counting on a paper calendar.

How it works

You pick a start date, choose add or subtract, enter an amount, and select the unit. The tool then applies the shift directly to the calendar:

Days — moves the date by exactly that many calendar days.
Weeks — moves it by the amount × 7 days (so “2 weeks” always equals 14 days, regardless of month boundaries).
Months — shifts the calendar month directly. If the result month has fewer days than the start day, the date rolls forward into the next month (for example, 31 January + 1 month = 3 March in a non-leap year, since February has 28 days and 31 − 28 = 3).
Years — shifts the calendar year. 29 February + 1 year in a non-leap year becomes 28 February.

The result shows as a full weekday-and-date string, so you know immediately whether the date lands on a weekend or working day.

Worked example

Start date 1 January 2026, add 90 days:

January has 31 days, so adding 90 days moves through the rest of January (30 days), all of February (28 days in 2026), and 32 days into March, landing on 1 April 2026. In 2026 that is a Wednesday.

Input	Value
Start date	1 Jan 2026
Operation	Add
Amount	90 days
Result	Wed, 1 Apr 2026

Practical uses and common date durations

Situation	Typical duration to add
Employment trial / notice period	30, 60, or 90 days
Invoice payment terms	14, 30, or 60 days
Return or refund window	14 or 30 days
Subscription renewal	30 days or 1 month
Contract or warranty end	1 or 2 years
Driving licence renewal	10 years
Passport validity	10 years

Month and year edge cases

The month-shift logic follows standard calendar convention. If you are computing a legal deadline — for example, a 6-month option period from 31 August — you may want to verify with a solicitor whether the deadline is 28 February or 2 March, as different legal jurisdictions handle the “last day of the month” question differently. For day-exact calculations, use days or weeks to avoid this ambiguity.

Everything runs entirely in your browser — nothing is uploaded.