Date Difference Calculator
Calculate the exact time between any two dates in days, weeks, months, and years.
The date difference calculator is one of the most-searched calculator tools because it comes up constantly in real life: how long until a contract expires, how many days since a purchase, how long ago something happened, whether a deadline is 30 or 45 business days from now. Having a tool that gives you days, weeks, months, weekdays, and weekend days all at once removes a lot of manual counting.
Business deadlines are often stated in "business days" or "weekdays" rather than calendar days. A 30-business-day deadline from Monday is not the same as 30 calendar days. This calculator shows both so you can convert correctly.
Why date math is harder than it looks
Calendar months have different lengths. Leap years add a day every four years (with exceptions for century years). Counting calendar months between dates is ambiguous when months have different day counts. This calculator counts exact calendar days as the base unit, then derives approximate months by dividing by 30.44 (average days per month) and exact years by comparing calendar dates.
Common uses
Contract and warranty expiration: most consumer warranties are 1 or 2 years from purchase date. Knowing the exact expiration in calendar days helps when a deadline is approaching. Loan terms: a 36-month auto loan from a specific start date ends on a specific day — date math confirms this. Lease agreements: month-to-month notice periods, lease termination dates. Employment: probationary periods, anniversary dates for raises or vesting. Legal: statutes of limitations, filing deadlines.
Frequently asked questions
How do I count business days excluding holidays?
This calculator counts weekdays (Monday through Friday) without excluding holidays, since holidays vary by country, state, and employer. For deadline calculations that exclude specific holidays, subtract the number of holidays that fall in the weekday count from the weekday total.
Is the start date included in the count?
This calculator counts from day 0 (start date) to day N (end date), so the total is the number of days elapsed. If a contract starts January 1 and ends January 31, the difference is 30 days. Whether "30 days from January 1" means January 30 or January 31 depends on whether the starting day counts as day 0 or day 1 — check your specific contract language.