How do I calculate the difference between two dates?

Choose the date-difference mode, enter a start date and an end date, and read the calendar years, months, days and total-day results.

Should I include the end date?

Use the inclusive option when both the first and last calendar dates should count as part of the period.

Can I add or subtract days from a date?

Yes. Switch to add/subtract days, enter the start date, and use a positive or negative day count.

Does this count business days?

No. It counts calendar days. Use a business-day calculator when weekends or holidays should be excluded.

Date Calculator

Calculate the date difference between two dates or add and subtract calendar days from a start date, with full calendar breakdowns.

Start date

End date

Include end dateAdds one calendar day to the interval. For legal, HR or filing deadlines, check the governing rules separately.

This calculator counts calendar days. Business days, holidays, medical timelines and legal deadlines require separate rule checks.

Date difference and date arithmetic

English date-calculator results usually combine two practical workflows: compare two calendar dates, or move a start date forward or backward by a number of days.

Δ d = ∣ D_{e n d} - D_{s t a r t} ∣ + I

I is 0 in standard date-difference mode and 1 when the end date is included.

What the result includes

Calendar difference in years, months and days.
Total days, full weeks, hours and minutes as supporting values.
Optional inclusive end-date counting for periods where both boundary dates count.
A separate add/subtract days mode for future or past date checks.

Calendar arithmetic only

The calculator does not apply business-day calendars, federal holidays, medical protocols or legal deadline rules.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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