Time Between Dates Calculator

What This Calculator Does

This Time Between Dates Calculator shows the duration between any two dates in several units at once. You get the total number of days, weeks, months, and years, a human-friendly breakdown like "2 years, 3 months, 12 days," and the exact business days, weekend count, hours, minutes, and seconds. Whether you are tracking a contract period, a relationship milestone, a project deadline, or a vacation countdown, every relevant unit is visible in a single card so you never need to recalculate.

Everything runs entirely in your browser with JavaScript Date math. Nothing is uploaded, logged, or stored. Default values show the span of one year (today to 365 days from today) so you can experiment immediately, and any change updates every result instantly.

How It Handles Months and Years

Months have different lengths (28, 29, 30, or 31 days), so a "month" is not a fixed number of days. This calculator uses calendar-based math: it rolls forward year-by-year and month-by-month from the start date, borrowing the previous month's day count when necessary. This matches the way legal contracts, leases, and court deadlines count months.

Leap years are handled automatically because the total-day figure is computed from the real timestamp difference. If a February 29 falls inside the range, it is counted as one day just like any other date.

Business Days

The business days figure counts every Monday through Friday inside the range, inclusive of both endpoints. Saturdays and Sundays are reported separately as the weekend count. The calculator does not subtract public holidays, because holidays vary by country, region, and industry — a US federal holiday is irrelevant in Korea, and vice versa. For exact working-day math in a specific jurisdiction, subtract your region's official holiday count from the business-day total.

Common Uses

• Age difference between two people, or the age at a specific past or future date.
• Project duration — how many working days remain until launch or delivery.
• Relationship milestones — days together, wedding anniversaries, dating anniversaries.
• Contract periods — leases, subscriptions, employment terms, notice periods.
• Historical spans — how many days ago an event happened, or how many hours until a countdown target.

Frequently Asked Questions

How does it calculate months if they have different lengths? It uses calendar math — rolling forward year-by-year and month-by-month from the start date — rather than assuming a fixed 30-day month. This matches how most legal and contractual date math is done.

Does it account for leap years? Yes. Total days are counted exactly, so leap years (divisible by 4, except centuries unless divisible by 400) are handled correctly.

Does business days include holidays? No. The business-day count only excludes Saturdays and Sundays. Public holidays vary by country and region, so they are not subtracted automatically — subtract your region's holiday count from the business-day total if you need exact working days.

Is my data stored? No. All calculations run entirely in your browser. No dates or data are sent to any server.