Date Calculator

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Date Calculator — Days Between Dates, Add or Subtract Time

Find out exactly how many days, weekdays, weeks, and months separate two dates — or add and subtract years, months, weeks, and days from any date. The calendar-aware math handles leap years and month lengths correctly (Jan 31 + 1 month is Feb 29 in 2024, not Mar 2).

Plan project deadlines, count down to events, calculate tenure or age in precise calendar terms, or check what date lands 90 days from a contract signing. All computation is local — no dates leave your browser.

How to calculate dates

  1. Switch between "Days between dates" and "Add / subtract" tabs.
  2. For differences: pick start and end dates and read totals instantly.
  3. For arithmetic: pick a base date, choose add or subtract, enter years/months/weeks/days.
  4. The resulting date shows with its weekday.

Frequently asked questions

How are weekdays counted?

Weekdays exclude Saturdays and Sundays. Note that public holidays are not excluded — they vary by country and would need a local holiday calendar.

How does month arithmetic handle short months?

When the target month is shorter, the day is clamped: Jan 31 + 1 month = Feb 29 (in 2024), and Mar 31 + 1 month = Apr 30. This matches how contracts and calendars conventionally treat "one month later".

Is a "month" 30 days here?

No — calendar months are used for the breakdown, while the "total months" figure is the whole number of calendar months between the dates. Day counts use exact calendar math including leap years.

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PureKit · date-calculator · Free online tool — files processed locally in your browser, no upload.