Date Difference Calculator

The calculator counts every calendar day from the start date to the end date. For example, January 1 to January 10 = 9 days (not counting the start date). To include both endpoints, add 1. The calculation accounts for varying month lengths (28-31 days) and leap years automatically.

Months vary from 28-31 days, so 'one month' isn't a fixed duration. January 31 to February 28 is technically 1 month, but only 28 days. March 1 to April 1 is also 1 month, but 31 days. Our calculator shows both the calendar month count and exact days so you can use whichever fits your needs.

Total days counts every calendar day including weekends and holidays. Working days (business days) counts only Monday-Friday, excluding weekends. For example, a 2-week period has 14 total days but only 10 working days. Note: public holidays vary by country and aren't automatically excluded.

Leap years add February 29th, making those years 366 days instead of 365. If your date range spans a leap year (2024, 2028, etc.), that extra day is automatically included. This matters for annual calculations—'one year' from February 29, 2024 lands on February 28, 2025 since Feb 29 doesn't exist in non-leap years.

Enter your project start and deadline to see total days available. The working days count helps estimate actual workdays for scheduling. For milestones like '100 days until launch' or 'how long since our founding', enter the dates and get instant clarity. Many project managers use this to verify timeline feasibility.