Days Between Dates Calculator
Count the exact number of days between any two dates — all calendar days, weekdays only, or business days (skipping US federal holidays). Pick whether to include both endpoints or just the difference.
Result
How to use this calculator
- Pick a start and end date. Order does not matter — the result is always positive.
- Choose exclusive (raw difference) or inclusive (+1 to count both ends) depending on what you are measuring.
- Use the breakdown lines to see the same gap expressed in weeks, months, or years.
About this calculator
Counting days between two dates is straightforward arithmetic — until you ask "how many business days?". This calculator does both. By default it counts every calendar day; switch "Which days to count" to "Weekdays" to skip Saturday/Sunday, or to "Business days" to also exclude US federal holidays (2024-2030 hardcoded). The classic inclusive/exclusive setting still applies: "Exclusive" reports just the difference (Mon → Tue = 1 day); "Inclusive" counts both endpoints (Mon → Tue = 2 days). For calendar-day counts the same weeks/months/years breakdown is shown.
What this calculator does
This calculator returns the number of calendar days between any two dates and lets you choose between exclusive counting (the raw gap — Monday to Tuesday is 1) and inclusive counting (both endpoints count — Monday to Tuesday is 2). It also expresses the same gap in weeks (decimal), months (using the 30.4375-day Gregorian average), and years (using 365.25 days/yr to absorb leap years). Order does not matter; the result is always positive. Both dates are interpreted as UTC midnight so the answer is independent of the browser's local time zone.
How it works — the formula
Days between two dates = (later − earlier) / 86,400,000 ms
UTC midnight on both endpointsCalendar-day arithmetic is the count of midnights between two ISO dates. Both dates interpreted as UTC midnight; the difference in milliseconds divided by 86,400,000 (ms per day) gives the count exactly because both endpoints sit on day boundaries. Inclusive vs exclusive counting is the only ambiguity: Monday-to-Tuesday is 1 day exclusive or 2 inclusive.
Worked examples
- Inputs:
- 2026-06-01 → 2026-06-15
- Output:
- 14 days exclusive (or 15 days inclusive)
Trip duration is normally counted inclusive of both arrival and departure — most travel insurance and rental contracts use the 15-day figure here.
- Inputs:
- 2026-05-08 → 2026-12-31
- Output:
- 237 days remaining
Contract deadlines usually use the exclusive count. "Within 237 days" means 237 sleeps until the end-of-year deadline.
- Inputs:
- 2025-12-15 → 2026-03-15
- Output:
- 90 days (2025 is not a leap year)
Crossing a year boundary the calendar-aware way: 16 + 31 + 28 + 15 = 90. The same span ending in 2024 would be 91 days because 2024 was a leap year.
When to use this vs other tools
Days Between Dates is the general date-arithmetic tool. For different units or for business-day counting, reach for a more specific tool.
- Weeks Between Dates
Use when you want an explicit "N weeks and M days" breakdown rather than a decimal weeks figure — useful for pregnancy tracking, sprint planning, and weekly billing.
- Months Between Dates
Use when the relevant period is a calendar month (rent, subscription, lease). Returns exact whole months because months are calendar-aware here, not approximated as 30.44 days.
- Business Days Calculator
Use when contracts or service-level agreements say "X business days" — excludes weekends and US federal holidays, which a raw day count does not.
- Age Calculator
Use for the special case where one endpoint is "today" — Age Calculator also splits the result into years + months + days and surfaces the day of the week of the start date.
Authority note
ISO 8601 is the international standard that defines how dates are represented and compared. IETF RFC 3339 is the internet-protocol profile of ISO 8601; together they are the references every modern programming-language date library implements. NIST publishes the US authoritative timekeeping reference, including the leap-year rules used here.
Limitations
- Time-zone-sensitive deadlines need evaluation in the relevant local zone — UTC midnight may shift the count by ±1.
- Inclusive vs exclusive counting matters: contracts often say "within 30 days" inclusive of the start day; check wording.
- Date strings without a time-zone offset are interpreted as local time by some libraries; this calculator treats them as UTC.
- For business-day counts (excluding weekends and holidays), use a separate business-day calculator.
Day counts are exact; only the inclusive/exclusive convention introduces ambiguity.