Calculate the exact number of days, weeks, months, and years between two dates. Add or subtract days from a date.
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Difference = End Date − Start Date (in milliseconds, converted to days)Total DaysCalendar days between datesWeekdaysMonday–Friday days onlyWeeksTotal days ÷ 7Date difference is calculated by converting both dates to Unix timestamps (milliseconds since January 1, 1970) and finding the difference. This approach automatically handles month length variations, leap years, and timezone considerations.
Date calculations are surprisingly complex due to varying month lengths, leap years, and different calendar systems. Whether you are counting down to a special event, calculating a project deadline, determining how long you have been in a relationship, or figuring out how many business days remain until a legal deadline, a reliable date difference calculator is invaluable.
Enter the start and end dates in YYYY-MM-DD format. The calculator computes the total calendar days, weekdays, weekend days, and expresses the difference in weeks, months, and years. The weekday count is particularly useful for business and legal applications.
| Duration | In days |
|---|---|
| 1 week | 7 days |
| 2 weeks | 14 days |
| 1 month (average) | ≈ 30.44 days |
| 3 months (quarter) | ≈ 91.3 days |
| 6 months | ≈ 182.6 days |
| 1 year (calendar) | 365 days (366 in a leap year) |
| 1 year (average) | ≈ 365.25 days |
A summer period — June (30) + July (31) + August (31).
92 days — a little over 13 weeks.
1 September to 30 September 2025 — counting weekdays only.
21 working days in that window.
Legal and financial deadlines are often in business days, not calendar days — this split matters.
This calculator handles all the complexity of date arithmetic - varying month lengths, leap years, and calendar irregularities - giving you accurate results instantly. The weekday count feature is especially valuable for project management and legal deadline calculations.
Ensure dates are entered in YYYY-MM-DD format. A common error is entering dates in different formats (e.g., one in MM/DD/YYYY and another in DD-MM-YYYY), which produces incorrect results. The calculator treats the earlier date as the start regardless of which field it is entered in.