Date Difference Calculator — Days, Hours, Business Days Between Dates

Pick two dates and instantly see the gap in every unit — years, months, weeks, days, hours, minutes, seconds, plus a calendar breakdown and a business-day count with optional US federal holiday exclusion.

Country

Exclude holidays

Start Date

End Date

Difference

Pick a start and end date.

What is a date difference calculator?

A date difference calculator takes two dates and returns the gap in every reasonable unit — years, months, days, hours, even business days that skip weekends and public holidays. Engineers use it to compute SLA windows, bill-by-the-day usage, retention periods, contract durations, and ages; project managers use it to plan around weekends and statutory days off.

This calculator gives both the exact calendar breakdown ("1 year, 2 months, 14 days") and the continuous decimal totals (e.g. 4.7368 years), plus a configurable business-day count that knows about US federal holidays for 2024-2027. The two date inputs read your browser's local zone, so output is unaffected by DST.

How to calculate date difference online — 4 steps

Pick a start date. Use the datetime-local input or click Now to use the current local time.
Pick an end date. Order does not matter — a negative interval is supported and clearly flagged.
Toggle business-day mode. Pick a country (currently US) and check Exclude holidays to trim federal observances.
Read the right panel. Calendar diff, every total unit, and business-day count are listed and update on every change.

Sample input / output

Start: 2024-01-15T09:00
End:   2025-04-30T17:30

Calendar:      1y 3mo 15d
Total days:    471.3542
Total hours:   11312.50
Total weeks:   67.3363
Total years ≈  1.2904
Business days: 337
Business days (− US holidays): 330

Calendar + Continuous

Exact calendar breakdown (years/months/days) AND continuous decimals in every unit. Use whichever the situation calls for.

Business-day count

Walks day by day, skipping Sat and Sun. Optional US federal holiday filter trims New Year, MLK, Memorial Day, July 4, Labor Day, Thanksgiving, Christmas.

Direction-aware

End-before-start produces a negative interval — useful for time-until-deadline. Click Swap to flip the inputs in one click.

Common use cases

check_circleComputing SLA response windows that exclude weekends
check_circleBilling customers by day for prorated subscription changes
check_circleCalculating age in years, months, and days for forms and reports
check_circleCounting business days remaining until a project deadline
check_circleWorking out lease, contract, or insurance period lengths
check_circleMeasuring incident MTTR (mean time to recovery) in hours
check_circleDetermining elapsed time since a feature launched
check_circleChecking how many working days a PTO request will consume

Calendar diff vs total days — which to use?

The two views answer different questions. Calendar diff ("1 year, 2 months, 14 days") is what humans say out loud — it walks the calendar exactly and is the right output for invoices, contracts, age statements, and "time since launch" labels. Total days as a decimal (471.3542) is right for math: prorating, charting, and sorting. The continuous "Total years" and "Total months" values use 365.25 and 30.4375 averages so they are useful for actuarial estimates but should not appear in user-facing copy without rounding to a whole unit.

Need other DateTime tools?

Pair the difference calculator with the rest of OpenFormatter's browser-side date and time toolkit.

Timezone Converter Duration Formatter Unix Timestamp Converter

Frequently Asked Questions

Why are "years" and "months" approximate?

Years vary between 365 and 366 days; months vary between 28 and 31 days. The "Total years" and "Total months" rows divide the millisecond gap by 365.25 and 30.4375 respectively, which is the average length over a 400-year Gregorian cycle. The "Calendar" breakdown ("1 year, 2 months, 14 days") is exact — it walks the calendar from start to end and counts whole years, then whole months, then leftover days.

How are leap years handled?

Leap years are handled implicitly because the calculator works with millisecond timestamps and JavaScript Date objects, both of which know the calendar. February 29 counts as one day; a span that crosses Feb 29 has one extra day compared to the same range in a non-leap year. The 365.25 divisor for "Total years" is an average, not an assumption that every year has the same length.

What is a business day?

In this calculator a business day is any day Monday-Friday that is not a public holiday (when the holiday filter is on). The count walks day by day from start to end, skipping Saturday (day 6) and Sunday (day 0). It does not skip the start date itself — only days strictly after start and up to and including end are counted.

Which holidays are excluded?

When the country is set to United States and Exclude holidays is on, seven federal holidays are skipped: New Year's Day, Martin Luther King Jr. Day, Memorial Day, Independence Day, Labor Day, Thanksgiving, and Christmas. The dates are pre-computed for 2024-2027 and use the observed date when the holiday falls on a weekend (e.g. July 4 2026 falls on a Saturday, observed July 3).

Can I use this to calculate age?

Yes — set start to the date of birth and end to today (click Now). The Calendar breakdown ("32 years, 4 months, 11 days") is the standard way to express age. The "Total years" decimal is useful for actuarial or scientific calculations where you need a continuous value.

How do I exclude weekends in different languages?

JavaScript: loop with date.getDay() and skip 0 (Sun) and 6 (Sat). Python: pandas.bdate_range(start, end) or numpy.busday_count(start, end). SQL (Postgres): generate_series(start, end, '1 day') filtered with EXTRACT(dow FROM d) NOT IN (0, 6). Excel: NETWORKDAYS(start, end, [holidays]). All of these treat the count as exclusive of the start, inclusive of the end — same convention as this tool.

Does this account for time zones?

The two datetime-local inputs are read in your browser's local time zone (no offset suffix). The millisecond difference is therefore zone-agnostic — a 24-hour gap is exactly 24 hours regardless of DST. If you need to compare across zones (e.g. 9 AM PST to 9 AM EST), convert both to UTC first using the Timezone Converter, then enter the UTC values here.

Why is end-before-start shown as negative?

A negative interval indicates the second date is earlier than the first — common when computing "time until deadline" for a deadline that has already passed. The Calendar field also shows a leading minus. If you would rather see absolute values, click Swap to flip the inputs in one click.