Date Calculator - Days Between Two Dates

To use this date calculator:

1. Enter the start year, start month, and start day.
2. Enter the end year, end month, and end day.
3. Toggle Include End Date to choose whether the end date counts as a full day.
4. Results appear instantly showing total days, complete weeks, remaining days, months, years, and approximate business days.

The calculator swaps dates automatically if the end date is earlier than the start date, so you always get a positive result.

A date calculator computes the duration between any two dates, expressed in days, weeks, months, and years. It is useful for project planning, tracking deadlines, counting down to events, or simply finding out how many days exist between two points in time.

Unlike basic subtraction of calendar dates, this calculator properly accounts for varying month lengths (28, 29, 30, or 31 days), leap years, and provides both a total day count and a broken-down view of weeks and remaining days.

The date calculation uses the following approach:

• Total Days: (End Date − Start Date) in milliseconds / 86,400,000 ms per day. Add 1 if including the end date.
• Weeks: Total Days / 7 (integer division).
• Remaining Days: Total Days mod 7.
• Months: Calendar month difference, adjusted for partial months.
• Years: Calendar year difference, adjusted if the anniversary has not yet occurred.
• Business Days: Total Days × 5 / 7 (rounded). This is an approximation that does not account for holidays.

Example 1: January 1, 2026 to December 31, 2026 (including end date): 365 days, 52 weeks and 1 day, 12 months, approximately 261 business days.

Example 2: March 15, 2026 to June 15, 2026 (including end date): 93 days, 13 weeks and 2 days, 3 months, approximately 66 business days.

Example 3: February 1, 2024 to March 1, 2024 (leap year, including end date): 30 days, 4 weeks and 2 days.