Add or subtract days, weeks, months or years from any date, with correct end-of-month handling.
Deadlines are almost always expressed as an offset: 15 days to appeal, 30 days to pay, 90 days of warranty, six months of probation, five years of validity. Counting that on a paper calendar is where mistakes happen — it is easy to lose a day crossing a month boundary or to forget that the month you land on is shorter than the one you started from. This tool does the arithmetic on the real calendar and shows the resulting date together with its weekday, which is usually the next thing you need to know.
Adding months and years needs a rule for impossible dates, and the tool uses the standard one: clamping. 31 January plus one month is 28 February (29 in a leap year), and 29 February plus one year is 28 February. That is how spreadsheets, databases and most legal deadlines behave, and the tool warns you on screen whenever the day was moved because the target month is shorter. Adding days and weeks needs no such rule — those are plain day counts.
The business-days option walks the calendar skipping Saturdays and Sundays, so 15 business days from a Thursday lands three weeks later. Public holidays are not removed: they change by country, state and city, and guessing them would produce confidently wrong deadlines. Treat the result as the weekday-only date and push it forward by the holidays that apply to you. As with every tool here, the calculation runs entirely in your browser.
Days and weeks: result = start + n (weeks × 7) counted directly on the calendar. Months and years: the month index is shifted by n (or n × 12) and the day is clamped to the last day of the target month. Business days: from a weekday, five business days equal seven calendar days; the remainder is stepped one day at a time, skipping Saturday and Sunday.
You get 28 February — or 29 February in a leap year. When the target month is shorter than the start day, the date is clamped to the last day of that month, which is the same rule spreadsheets and most contracts use.
No. It only skips Saturdays and Sundays. Holidays differ by country and city, so add them yourself on top of the result.
No, it starts the following day. Adding 1 day to 10 March gives 11 March, which is how deadlines counted "from" a date normally work.
Yes. Choose "Subtract" to walk the calendar in reverse — handy for finding when a period started from its end date.
No. Everything is computed locally in JavaScript; the page makes no network requests with your data.
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