About this tool
A date difference calculator counts the number of days, weeks, months, or years between two calendar dates. Unlike simple subtraction, it correctly handles months of different lengths, leap years, and calendar irregularities.
This tool gives you both calendar days (every day counted) and business days (Monday to Friday only, excluding weekends). The business-day mode is especially useful for project deadlines, contract dates, and any planning where weekends do not count.
How to use it
- 1Pick the start date.
- 2Pick the end date.
- 3Toggle between "Calendar days" and "Business days" to switch counting modes.
- 4Review the breakdown in years, months, weeks, and days for a fuller picture.
Common use cases
- Counting days until a deadline, due date, or wedding
- Calculating project duration for billing or planning
- Counting business days between contract signing and delivery
- Tracking how long since a major event (a job started, a relationship began, a baby was born)
- Counting paid time off, vacation days, or notice periods
How it works
Calendar days are computed by subtracting the two dates as UTC timestamps and dividing by 86,400 seconds per day.
Business days are computed by iterating each day between the two dates and excluding Saturday and Sunday. Public holidays are not subtracted automatically since they vary by country.
Frequently asked questions
Does it include the start date or the end date?
It counts the difference between them, so if you pick today and tomorrow, the result is 1 day. If both dates are the same, the result is 0.
Are weekends excluded from business days?
Yes. The business-day mode counts only Monday through Friday. Public holidays are not automatically excluded as they differ by region.
How are leap years handled?
Correctly. Leap days (February 29) are counted as normal days. For year-level differences, the tool respects the actual number of days each year.
Can I calculate negative differences (going backward in time)?
Yes. If the end date is before the start date, the tool shows the magnitude of the difference. The order is just for display.