Date Difference Calculator
The Date Difference Calculator calculates the time between two dates in days, weeks, months, and years. It is useful for project planning, age calculation, contract duration, countdown to events, and any scenario where you need to know the exact time between dates. The calculator accounts for leap years and provides precise results. It can also add or subtract days from a date to find a future or past date.
Formula
Date difference: - Days: absolute difference in days - Weeks: days / 7 - Months: calendar months between dates - Years: calendar years between dates - Business days: excludes weekends Leap years: February has 29 days Leap year: divisible by 4, not 100, unless 400
Example
From: 2026-01-01 To: 2026-09-09 Difference: Days: 251 Weeks: 35.86 Months: 8.3 Years: 0.69 Business days: 179
How to Use
- Enter the start date
- Enter the end date
- The calculator shows the difference in days, weeks, months, and years
- Optionally calculate business days
- Or use the add/subtract feature to find a future or past date
Frequently Asked Questions
How is the date difference calculated?
The calculator converts both dates to timestamps (milliseconds since Unix epoch) and finds the absolute difference. This is then converted to days, weeks, months, and years. The calculation accounts for leap years and varying month lengths.
Does the calculator include or exclude the start/end date?
By default, the calculator counts the number of days between dates (exclusive of both endpoints). For example, from Jan 1 to Jan 3 is 2 days. You can configure it to be inclusive if needed.
How are business days calculated?
Business days exclude Saturdays and Sundays. The calculator counts only Monday through Friday. Holidays are not accounted for as they vary by country and year. For holiday-aware calculations, use a dedicated business day calculator.
Can I add or subtract days from a date?
Yes. The calculator can add or subtract a specified number of days, weeks, or months from a date. For example, adding 90 days to 2026-01-01 gives 2026-04-01. This is useful for calculating due dates and deadlines.
Does the calculator handle time zones?
The calculator works with dates only (no time component), so time zones do not affect the result. If you need time zone-aware calculations, include the time and specify the time zone. For most date difference use cases, time zones are not relevant.