Date Calculator

This free date calculator computes the difference between two dates. It can also add to or subtract from a date.

How to Use the Date Calculator

Use the Date Difference tab to find how many days, weeks, months, and business days lie between two dates. Toggle "Include end date" to count inclusively. Switch to the Add / Subtract tab to add or remove years, months, weeks, or days from any starting date.

Formula: Date difference = |End Date − Start Date| in milliseconds ÷ 86,400,000. Business days exclude Saturdays and Sundays.

Frequently Asked Questions

What counts as a business day?+

The calculator counts every weekday (Monday–Friday) between the two dates, excluding Saturdays and Sundays. It does not automatically exclude public holidays.

Does "include end date" matter?+

Yes. For example, Jan 1 to Jan 3 is 2 days without the end date or 3 days with it included (counting both endpoints).

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