Date Calculator

Easily find the exact duration between two dates, or add/subtract days, weeks, months, and years to find a future or past date.

Start Date

End Date

Key Takeaways & Quick Facts

Primary Purpose

Calculate days between dates or add/subtract time.

Execution Environment

100% Client-Side In-Browser (Zero Cloud Uploads)

Standard Verification

Calculations tested against standard benchmarks

How to Use Date Calculator

To find the difference between two dates, use the "Date Difference" tab. Select a start and end date to see the total days and calendar difference.
To add or subtract time from a date, use the "Add/Subtract Time" tab. Enter a starting date, the amount of time, and the unit (days, weeks, months, years).
Business days (excluding Saturdays and Sundays) are also calculated automatically in the Date Difference tab.

How it Works

The Date Calculator uses pure calendar arithmetic, operating on UTC dates to prevent errors caused by daylight saving time shifts. When adding months or years, it strictly respects calendar boundaries (e.g., adding one month to January 31st results in the last day of February).

Examples

Input: Difference between Jan 1, 2024 and Jan 10, 2024

Result: 9 Days

Input: Add 6 months to Aug 15, 2024

Result: Feb 15, 2025

Frequently Asked Questions

Are the end dates inclusive or exclusive?

By standard mathematical convention, the date difference is exclusive of the end date. For example, the difference between Jan 1 and Jan 2 is exactly 1 day.

Does this calculator exclude public holidays for business days?

No. The business days calculation strictly excludes weekends (Saturdays and Sundays). It does not account for regional public holidays, as these vary wildly by country and state.

How does it handle leap years?

The calculator uses the native calendar engine which perfectly understands leap years. February 29th is accurately accounted for in all date additions and differences.

Formula Audited & Client-Side Private

Calculations are verified against standard mathematical and banking benchmarks. Data stays on your device in local memory.

Our Verification Standards →