Date calculator

Use the date calculator to add or subtract days, weeks, months or years from any date.

Choose a starting date, select whether you want to add or subtract time, enter a value and see the resulting date instantly.

Find the weekday for any date

Weekday —

Add or subtract time from a date

The calculator can move forward or backward from any selected date.

You can calculate:

  • Days from a date
  • Weeks from a date
  • Months from a date
  • Years from a date
  • Dates in the past
  • Dates in the future

The result also shows the weekday, ISO week number and common date formats.

How to use the date calculator

  1. Select a starting date.
  2. Choose Add or Subtract.
  3. Enter a number.
  4. Choose days, weeks, months or years.
  5. Select Calculate date.

The resulting date is shown immediately below the calculator.

Add days to a date

Adding days is useful when calculating deadlines, delivery dates, appointment dates or future events.

For example, if you add 30 days to a starting date, the calculator moves forward exactly 30 calendar days.

Weekends are included in this calculation.

If you need to exclude weekends, use the Business Days Calculator.

Subtract days from a date

You can also calculate a date in the past.

For example, subtracting 90 days from a date can help determine an earlier deadline, historical reference date or previous reporting period.

Add weeks to a date

One week contains seven calendar days.

Adding:

  • 1 week adds 7 days.
  • 4 weeks adds 28 days.
  • 12 weeks adds 84 days.

The calculator handles this automatically.

Add months to a date

Months have different lengths, so adding months is not always the same as adding a fixed number of days.

For example:

  • January has 31 days.
  • February has 28 or 29 days.
  • April has 30 days.

The calculator uses calendar-based month arithmetic rather than assuming that every month contains the same number of days.

Add years to a date

Adding years is useful for anniversaries, contracts, long-term planning and age-related calculations.

The calculator also handles leap years when possible.

For example, adding one year to February 29 in a leap year may result in the final valid day of February in a non-leap year.

Result date formats

The result is displayed in several common formats:

  • MM/DD/YYYY – commonly used in the United States
  • DD/MM/YYYY – commonly used in the United Kingdom and many other countries
  • YYYY-MM-DD – ISO format
  • Full written date
  • Weekday
  • ISO week number

Calendar days vs business days

This calculator uses calendar days.

That means all days are counted, including:

  • Monday
  • Tuesday
  • Wednesday
  • Thursday
  • Friday
  • Saturday
  • Sunday

If you need to count only Monday through Friday, use the Business Days Calculator.

Find the weekday for any date

The calculator also includes a weekday finder.

Choose any date to see which day of the week it falls on.

This can answer questions such as:

  • What weekday was I born?
  • What day of the week is my birthday this year?
  • What weekday was a historical date?
  • What weekday will a future event occur?

Related date tools

You may also find these useful:

Frequently asked questions

Can I add days to a date?

Yes. Choose Add, enter the number of days and select Days.

Can I subtract days from a date?

Yes. Choose Subtract to move backward from the selected starting date.

Can I add months instead of days?

Yes. The calculator supports days, weeks, months and years.

Are weekends included?

Yes. This calculator uses calendar days, so Saturdays and Sundays are included.

Does the calculator handle leap years?

Yes. Leap years are handled automatically.

Can I calculate a weekday for any date?

Yes. Use the weekday finder below the main calculator.

Does the calculator work for past dates?

Yes. You can select a past date or subtract time from any selected date.