Date Difference Calculator
Calculate the number of days, weeks, months, and years between two dates.
Updated April 2026 · CalcFlow Editorial
Enter values above and click Calculate to see your results.
What is a Date Difference? A date difference calculator computes the exact number of days, weeks, months, and years between two calendar dates, and optionally counts only business days (Monday through Friday).
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Rule of Thumb
A standard year has 365 days, 52 weeks, and approximately 261 business days. A month averages 30.44 days. Use business days for deadline calculations in work or legal contexts.
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Example Calculation
From January 1, 2020 to April 16, 2026 is 2,297 days, 328 weeks, or approximately 75 months and 15 days.
Key Facts
- •Leap years (every 4 years) add an extra day in February, affecting multi-year calculations.
- •The US legal system often counts calendar days for deadlines unless statutes specify business days.
- •A 30-day notice period from April 1 expires May 1 — not May 31.
How to Use
- Enter the start year, month (1-12), and day.
- Enter the end year, month, and day.
- Click Calculate to see the difference in days, weeks, months, and years.
- Business days excludes Saturdays and Sundays (no holiday adjustment).
Formula
Days = (End Date - Start Date) / 86,400,000 ms | Business Days = Count of Mon-Fri between dates| Period | Calendar Days | Business Days (approx) | Weeks (approx) |
|---|---|---|---|
| 1 month | 30-31 | 21-23 | 4.3 |
| 3 months | 90-92 | 65 | 13 |
| 6 months | 181-184 | 130 | 26 |
| 1 year | 365-366 | 261 | 52 |
| 2 years | 730-731 | 522 | 104 |
| 5 years | 1,826-1,827 | 1,304 | 261 |
| 10 years | 3,652-3,653 | 2,609 | 522 |