Date Calculator

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Date Calculator

Add or subtract days, weeks, months, or years, calculate date intervals, and estimate workdays with automatic leap-year and month-length handling
Quick Dates
Result Date
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Month/year adjustments use calendar months. If the target month does not have the original day, the last day of that month is used. For example, 2026-01-31 + 1 month = 2026-02-28.
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Days Difference
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Weeks Difference (Approx.)
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Years, Months, Days
By default, the natural-day difference between two dates is calculated without including the start date (for example, September 6 to September 13 is 7 days). To include both dates, add 1 to the day count.
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The current version treats Monday-Friday as workdays and does not include public holidays or adjusted workdays. Holiday data will be added in a future version.

Calculate date additions, date differences and time intervals

Online Date Calculator

The Date Calculator provides date addition, date subtraction and date interval calculations for quickly determining target dates and the time between two dates.

Date Addition and Subtraction

Enter a date and the number of days to add or subtract to calculate the target date. The calculator automatically handles different month lengths, year changes and leap years.

Date Difference

Enter a start date and an end date to calculate the difference in days and weeks, as well as the corresponding year-month-day difference.

Common Uses

The calculator is useful for project deadlines, contract periods, travel planning, anniversaries, schedules and everyday date calculations.

What is a date calculator?

A date calculator handles date addition, subtraction and date interval calculations. Enter a date and a number of days to find a target date, or enter two dates to calculate the difference in days, weeks and years, months and days.
  • Add or subtract any number of days from a specified date.
  • Automatically handle month changes, year transitions and leap years.
  • Calculate the number of days and weeks between two dates.
  • Show date differences in years, months and days for easier interpretation.
  • Provide quick date shortcuts such as today, tomorrow and seven days later.
Date calculations are useful for project schedules, travel plans, contract periods, anniversaries and everyday planning, using standard Gregorian calendar rules.
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