Date Plus Days Calculator (Future or Past Date)
Add or subtract a number of days from a date to find the resulting date, in calendar days or business days (skipping weekends), with the weekday shown. Runs in your browser.
Adds (or subtracts) the given number of days from the start date. In calendar mode every day counts; in business-days mode only Monday–Friday are counted, skipping weekends (public holidays are not excluded — see the workdays calculator for that). Dates are computed at midday so daylight-saving transitions never shift the result. Everything runs in your browser.
About this tool
Often you know a starting date and a number of days and need the resulting date: a deadline that is 90 days out, a return date 14 days from shipping, a 30-day notice period, or a date a certain number of days in the past. This calculator does that arithmetic in both directions and in two counting modes. In calendar-days mode it simply adds (or subtracts) the number of days, counting every day including weekends — so 30 days from January 1 lands on January 31. In business-days mode it counts only Monday through Friday, stepping over Saturdays and Sundays, which is what many contracts, payment terms, and processing windows mean by 'days'; note that this mode skips weekends but does not exclude public holidays, so for a holiday-aware count use the dedicated workdays calculator. You can add to reach a future date or subtract to find a past one, and the result is shown as a full date with its day of the week (handy for knowing whether a deadline lands on a weekend) plus an ISO format you can copy. The date math is handled carefully: dates are anchored at midday rather than midnight so that daylight-saving-time transitions — when a calendar day is 23 or 25 hours long — can never push the result onto the wrong day, a subtle error that affects many naive date calculators. Month lengths and leap years are handled automatically by the date engine, so adding days across month and year boundaries (including February in leap years) works correctly. Everything is computed locally; nothing is uploaded.
How to use it
- Pick the start date.
- Enter the number of days.
- Choose Add (future) or Subtract (past).
- Choose calendar days (count everything) or business days (skip weekends).
- Read the resulting date, its weekday, and the ISO date to copy.
Frequently asked questions
- How do I add days to a date?
- Enter the start date and the number of days and choose "Add." Calendar mode counts every day (30 days from Jan 1 is Jan 31); business mode counts only weekdays, skipping Saturdays and Sundays.
- What is the difference between calendar days and business days here?
- Calendar days count every day including weekends. Business days count only Monday–Friday, stepping over weekends. Business mode here does not skip public holidays — use the workdays-between tool for holiday-aware counts.
- Can I find a date in the past?
- Yes. Choose "Subtract (past)" and the tool counts backward from the start date by the number of days, in either calendar or business mode.
- Does it handle month lengths and leap years?
- Yes. Adding or subtracting days correctly rolls across months and years, accounting for 28/29/30/31-day months and leap years automatically.
- Why anchor dates at midday?
- Computing dates from midnight can land on a daylight-saving transition and shift the result by a day. Anchoring at midday keeps the date clear of that boundary, so the answer is always correct.
- Is anything uploaded?
- No. All calculations run entirely in your browser.