Date Difference Calculator

Date Difference Calculator — Exact Time Between Any Two Dates

How many days until the deadline? How long have you worked here? How old is the invoice? Counting on fingers across month boundaries and leap years fails fast. This free calculator gives the exact difference between any two dates — as total days, weeks + days, months + days, and years — plus a business-days mode that skips weekends. Instant, in-browser, no signup.

Why Date Math Is Harder Than It Looks

Months run 28–31 days, leap years insert February 29 on a divisible-by-4-except-centuries-unless-divisible-by-400 rule, and "a month later" from January 31 has no obvious answer. Software gets this wrong constantly — famous bugs have shipped from adding "30 days" as "1 month." This tool does the calendar-aware arithmetic correctly, including spans that cross multiple leap years.

Inclusive vs Exclusive Counting

From July 1 to July 5: exclusive counting says 4 days (nights between, hotel-style); inclusive says 5 days (both endpoints, rental-car and prescription-style). Contracts, billing systems, and law each have their own convention — the toggle lets you match whichever your document uses, and knowing the distinction prevents off-by-one disputes.

Common Calculations

• Project management — working days remaining to a launch date (weekends excluded).
• HR and payroll — exact tenure for benefits eligibility, notice periods, probation ends.
• Finance — days outstanding on invoices, interest accrual periods, contract terms.
• Personal — precise age in days, countdowns to events, anniversary math.
• Legal — statute deadlines and filing windows, where inclusive/exclusive counting genuinely matters.

Quick Reference: Common Spans

Free and Instant

All computation runs locally in your browser — unlimited date pairs, no account, nothing stored.