Instantly calculate the precise duration between two dates. Ideal for project planning, legal deadlines, and tracking age or events.
End date is earlier than start date.
Best for project durations. Leave unchecked for counting nights.
Total Days
Sunrises between dates
Calendar Duration
Full Y/M/D breakdown
Working Days
Excluding weekends
Alternative Units
Visual Breakdown: This chart illustrates the ratio of working days (Mon-Fri) versus weekend days (Sat-Sun) within your selected period.
Calculating duration accurately requires accounting for the Earth's orbit, which takes approximately 365.25 days. To keep our calendar aligned, we add an extra day—February 29th—every four years. However, a year divisible by 100 is not a leap year unless it is also divisible by 400. This calculator automates this complex logic for any date range up to the year 9999, ensuring your count is precise.
Exclusive counting (default) calculates the number of nights or 'gaps' between dates. Inclusive counting includes both the first and last day.
Yes. The calculator logic automatically detects leap years (including the 100/400 year rules) and adds February 29th to the count where appropriate.
Methodology: Calculations utilize the ISO 8601 date standard and the Proleptic Gregorian Calendar logic.
Disclaimer: While highly accurate, this tool is for informational purposes. Please verify critical legal deadlines with secondary sources.