Date Difference
Days between two dates
About This Calculator
Date difference calculates the number of days, weeks, months, or years between two dates. It is useful for calculating how long until a deadline, how many days have passed since an event, contract durations, and age calculations. Date arithmetic must account for varying month lengths and leap years.
Formula
Days between = End date − Start date (in calendar days)
Weeks = Days / 7
Months ≈ Days / 30.44 (average month length)
Years ≈ Days / 365.25 (accounting for leap years)
Example Calculation
Days between March 15, 2024 and November 28, 2024
- March 15 → March 31 = 16 days
- April through October = 214 days
- November 1 → November 28 = 28 days
- Total = 16 + 214 + 28 = 258 days
258 days, 36 weeks and 6 days, about 8.5 months
Common Date Intervals
| Interval | Exact Days | Weeks | Approx Months |
|---|---|---|---|
| 1 month (avg) | 30.44 | 4.35 | 1 |
| 1 quarter | 91.25 | 13.0 | 3 |
| 6 months | 182.5 | 26.1 | 6 |
| 1 year | 365.25 | 52.18 | 12 |
| 2 years | 730.5 | 104.4 | 24 |
| 5 years | 1826.25 | 260.9 | 60 |
Frequently Asked Questions
Does the calculator include the start date?
Convention varies: 'from Jan 1 to Jan 3' is either 2 days (exclusive) or 3 days (inclusive). Most date difference calculators use the exclusive convention (Jan 1 to Jan 3 = 2 days). Check which convention you need for your specific use case.
How do I calculate the number of business days between dates?
Subtract weekend days from the total calendar days, then subtract any public holidays in the period. The business days calculator handles this automatically.
How are months counted when they have different lengths?
When counting 'months between' two dates, software typically counts whole calendar months. From Jan 31 to March 31 is 2 months exactly. From Jan 31 to March 28 might be 1 month 28 days depending on the calculation method used.
What is the difference between calendar days and elapsed time?
Calendar days count from midnight to midnight. Elapsed time counts actual hours and minutes. If you depart Jan 1 at 11 PM and arrive Jan 3 at 1 AM, that is 1 calendar day gap but 26 hours elapsed time. Date difference tools typically use calendar days.