Date Calculator - Add or Subtract Days
Add or subtract days from a date
Use this free Add Days to Date Calculator whenever a deadline, delivery window or countdown is expressed in days rather than a calendar date: pick a start date, type how many days to move, choose add or subtract, and it gives you the exact landing date together with its day of the week. It rolls correctly across month ends, leap years and year boundaries, and the quick buttons cover the spans people ask for most - 7, 30, 90 and 365 days. Turn on the business-days option and it counts only Monday to Friday, skipping Saturdays and Sundays, which is how payment terms, delivery promises and "10 business days" notices are actually meant.
Business-day counting is where most people go wrong doing this by hand, because weekends stretch a span more than intuition suggests: 30 business days from a Friday is not about a month later but a full 42 calendar days away, because every block of 5 business days consumes a whole calendar week. This calculator walks the calendar one day at a time, so the count is exact, and it tells you how many weekend days were skipped and how many calendar days the span really covers. Everything runs in your browser - the dates you enter are never uploaded or stored. To find the gap between two dates you already know, use the Date Difference Calculator instead; this tool is the other half of the pair, starting from one date and a number of days.
How to use
- Pick the date you are counting from in the start date box.
- Type the number of days to move, or tap a quick button for 7, 30, 90 or 365 days.
- Choose Add days to look forwards or Subtract days to look backwards.
- Tick "Business days only" if the span should skip weekends, as in "within 10 business days".
- Click Calculate the date and read the result with its day of the week.
Frequently asked questions
What date is 30 days from today?
Set the start date to today, type 30, leave Add selected and click Calculate. Because months vary in length there is no fixed answer - 30 days from late January lands at the start of March in a normal year - which is exactly why a calculator beats counting on your fingers.
How does the business days option work?
With the option ticked, the tool steps through the calendar counting only Monday to Friday as days that "use up" your number, and Saturdays and Sundays are passed over. It also reports how many weekend days were skipped, so you can see the true calendar length of the span. Public holidays are not skipped, because they differ by country and state.
Can I count backwards, for example 90 days before a deadline?
Yes. Choose Subtract days in the Operation menu and enter 90 - the tool walks backwards from the start date with the same month-end and leap-year accuracy. This is the usual way to work out when to start something that must finish on a fixed date.
Does the result include the start date itself?
No - it counts whole days moved, so adding 1 day to a Monday gives Tuesday. That matches invoices, contracts and delivery estimates. If you need an inclusive count where both the first and last day count, add one extra day to your number.
What is the difference between this and the Date Difference Calculator?
This calculator starts with one date plus a number of days and finds the other date. The Date Difference Calculator starts with two dates and finds the number of days between them. Between them they answer every date-sum question in both directions.
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