Date Calculator
Free online date calculator. Add or subtract days, weeks, months, or years from any date, or find the exact difference between two dates.
How to Use the Date Calculator
Switch between Add/Subtract and Date Difference modes using the tabs. In Add/Subtract mode, pick a start date, enter a number, choose units (days, weeks, months, or years), and toggle add or subtract. In Date Difference mode, pick two dates to see the exact time between them.
About This Tool
Perform date arithmetic — add or subtract days, weeks, months, or years from any date, or find the exact difference between two dates in multiple units. Useful for project planning, deadline tracking, and event scheduling. Pair with Days Between Dates for quick day counts or Day of the Week Calculator to find what day a date falls on.
Quick Reference Table
| Duration | Days |
|---|---|
| 1 week | 7 |
| 2 weeks | 14 |
| 1 month (avg) | 30.44 |
| 3 months (avg) | 91.31 |
| 6 months (avg) | 182.62 |
| 1 year | 365 |
| 1 leap year | 366 |
| 1 decade | 3,652 |
Frequently Asked Questions
Does this calculator account for leap years?
Yes. All calculations use the JavaScript Date API which correctly handles leap years, varying month lengths, and calendar rules.
Can I calculate business days only?
The Date Difference mode shows total calendar days. For business-day calculations, use the Days Between Dates tool which includes a business-days toggle.
What is the date range limit?
The JavaScript Date object supports dates from roughly 271,821 BCE to 275,760 CE, far beyond practical use.
Is my data stored?
No. All calculations happen locally in your browser. Nothing is sent to any server.