Date Difference Calculator

A date difference calculator (also called a duration or days-between calculator) measures the elapsed time between two calendar dates and expresses it in convenient units — total days, weeks, months, years, or business days. The simple subtraction is harder than it looks: months have unequal lengths (28-31 days), leap years insert Feb 29 every four years (with century-year exceptions), and “business days” means different things in different countries because public-holiday calendars vary. This calculator handles all three: pure calendar math via the proleptic Gregorian rules, weekend exclusion built in, and national holidays for the US, UK, India, Germany, and Australia bundled out of the box. Pair it with the Working Days Calculator for “add N business days from a date”, the Days Until Calculator for live countdowns, or the Age Calculator for a full birth breakdown.