Frequently Asked Questions
How do you count days between dates? ▼
Subtract the earlier date from the later date to get the total number of milliseconds, then divide by 86,400,000 (milliseconds per day). The "include end date" option adds 1 to count both the start and end days — useful for counting inclusive durations like "how many days of vacation".
What counts as a business day? ▼
Business days are Monday through Friday, excluding weekends. This calculator does not subtract public holidays since they vary by country and region. For deadline calculations, always double-check for any holidays in your jurisdiction.
Why might the months count seem off? ▼
Months vary in length (28–31 days), so "2 months" from January 31 is different from "2 months" from February 28. This calculator computes calendar months by tracking year/month/day positions, not by dividing total days by 30.
Can I calculate how old someone is? ▼
Yes — set the start date to a birthdate and the end date to today. For a dedicated age calculator with birthday countdown and more details, try our Age Calculator tool.
What is the maximum date range this supports? ▼
This tool uses JavaScript's built-in Date object which supports dates from roughly 271,821 BCE to 275,760 CE — far more than any practical use case requires.