Date & Time

Date Difference Calculator

Pick any two dates and get the difference in years, months, days, weeks, business days, and total hours — plus whether the end date is past or future.

Start date

End date

Pick a start and end date to see the full difference.

What is a Date Difference Calculator?

A date difference calculator measures the time between two calendar dates using the Gregorian calendar the world has used since 1582. This tool reports the gap six ways — years/months/days (the calendar format a project plan uses), total days (for deadline tracking), total weeks and hours, and the business-day count with weekends split out. Leap years are handled correctly, month lengths are respected, and the direction indicator tells you whether the end date falls before or after the start. All calculations happen on-device in plain JavaScript; nothing you type is sent to a server.

How to use the Date Difference Calculator

1
Pick the start date
Use the first date picker. Any valid Gregorian date from 1000 CE onward works; the today button fills the current date quickly.
2
Pick the end date
The second date can be before or after the start — the tool reports the absolute difference either way and flags the direction.
3
Read the calendar breakdown
The years-months-days view is the format most contracts, travel plans, and legal documents expect.
4
Check the total units
Use total days for deadlines, total weeks for sprint planning, or the business-day count for SLA and payroll calculations.
5
Swap, reset, or recalculate
Swap flips the two dates, reset clears them, and changing either input recomputes everything instantly.

How the difference is calculated

Let d1 = start date, d2 = end date (both interpreted as local midnight).
 
Total days    = floor((d2 − d1) / 86,400,000 ms)
Total weeks   = total days / 7
Total hours   = total days × 24
 
Years/Months/Days (calendar):
  y = d2.year − d1.year
  m = d2.month − d1.month; if d2.day < d1.day, borrow from m
  d = days remaining in that month window
 
Business days = walk each day, count where dayOfWeek is 1–5

The simple millisecond subtraction is the authoritative total-day count — it handles leap days and month-length variation automatically. The years-months-days breakdown is a human-calendar interpretation and follows the borrow-from-next-unit convention used by `DATEDIF` in Excel and most civil-law contracts. Business days are computed by iterating through the interval and counting each weekday (public holidays are not subtracted — add them manually if your jurisdiction requires them).

Reference: Gregorian calendar — NIST Time & Frequency

Examples

Range	Difference
2025-01-01 → 2026-01-01	1 year · 0 months · 0 days · 365 total days · 261 business days A calendar year covering one non-leap year.
2024-02-28 → 2024-03-01	0 years · 0 months · 2 days · 2 total days Spans the Feb-29 leap day in 2024 — counted correctly.
2026-04-21 → 2026-06-15	0 years · 1 month · 25 days · 55 total days · 40 business days Typical project sprint window with weekend days excluded.

Common use cases

Plan project timelines and measure sprint durations in business days
Calculate notice periods, probation windows, or statute-of-limitations deadlines
Work out how many days until a wedding, vacation, or product launch
Age historical events or items by computing days since an anchor date
Verify payroll periods, billing cycles, or subscription renewals
Fill in form fields that require 'time employed' in years and months
Estimate travel itineraries where lodging is priced per business day

Related tools

Age Calculator

Calculate your exact age in years, months, and days from any date of birth.

BMI Calculator

Check body mass index from height and weight using metric or imperial units.

Percentage Calculator

Work out percentages, percentage change, and percentage of a total in seconds.

Tip Calculator

Add a tip, split the bill, and share the total evenly across a group.

Frequently asked questions

Does the tool count the start day, the end day, or both?

It measures the interval between the two dates as points in time, not the number of calendar days 'inclusive' on each end. For a start of Monday and an end of Friday you get 4 total days. If you need to include both endpoints, add one to the total.

Are public holidays excluded from business-day counts?

No — business days simply means Mon–Fri here. Public holidays vary widely by country and region, so the tool stays neutral. Subtract your jurisdiction's holidays manually, or use the total-days figure and count the holidays separately.

Does the calculation handle leap years?

Yes. The year difference follows the Gregorian leap-year rule (every 4 years, except century years unless divisible by 400), and intervals crossing February 29 are counted accurately because the underlying math works in milliseconds.

Why do some month combinations give 30-day months and others 31-day months?

Because months have varied lengths — January has 31 days, April has 30, February has 28 or 29. The years-months-days breakdown respects real calendar months, so the number of days in the 'remaining days' column depends on which month the interval ends in.

What time zone does the tool use?

Your browser's local time zone. Both dates are interpreted at midnight local time, so a difference of 7 calendar days always equals 7, regardless of daylight-saving-time transitions inside that window.

Can I pick dates before 1900 or in the year 3000?

Yes — the calculator accepts any valid date that JavaScript's `Date` object can represent, which covers roughly 271,800 BCE through 273,400 CE. Historical dates before the 1582 Gregorian switch are still computed as if the modern calendar had always been in use.

Why does the result sometimes say '0 years, 0 months, 30 days' instead of '1 month'?

Because a calendar month isn't a fixed 30 days. An interval from March 15 to April 14 spans 30 days but falls just short of a full calendar month, so the calendar breakdown reports 30 days; April 15 would tip it to exactly 1 month.

Is the start date or end date inclusive when I use the business-day count?

The start date is included if it's a weekday; the end date is also included if it's a weekday. So Mon → Fri of the same week returns 5 business days.

Last updated 2026-04-21

What is a Date Difference Calculator?

How to use the Date Difference Calculator

Pick the start date

Use the first date picker. Any valid Gregorian date from 1000 CE onward works; the today button fills the current date quickly.

Pick the end date

The second date can be before or after the start — the tool reports the absolute difference either way and flags the direction.

Read the calendar breakdown

The years-months-days view is the format most contracts, travel plans, and legal documents expect.

Check the total units

Use total days for deadlines, total weeks for sprint planning, or the business-day count for SLA and payroll calculations.

Swap, reset, or recalculate

Swap flips the two dates, reset clears them, and changing either input recomputes everything instantly.

How the difference is calculated

Let d1 = start date, d2 = end date (both interpreted as local midnight).
 
Total days    = floor((d2 − d1) / 86,400,000 ms)
Total weeks   = total days / 7
Total hours   = total days × 24
 
Years/Months/Days (calendar):
  y = d2.year − d1.year
  m = d2.month − d1.month; if d2.day < d1.day, borrow from m
  d = days remaining in that month window
 
Business days = walk each day, count where dayOfWeek is 1–5

Examples

Range	Difference
2025-01-01 → 2026-01-01	1 year · 0 months · 0 days · 365 total days · 261 business days A calendar year covering one non-leap year.
2024-02-28 → 2024-03-01	0 years · 0 months · 2 days · 2 total days Spans the Feb-29 leap day in 2024 — counted correctly.
2026-04-21 → 2026-06-15	0 years · 1 month · 25 days · 55 total days · 40 business days Typical project sprint window with weekend days excluded.

Common use cases

Plan project timelines and measure sprint durations in business days

Calculate notice periods, probation windows, or statute-of-limitations deadlines

Work out how many days until a wedding, vacation, or product launch

Age historical events or items by computing days since an anchor date

Verify payroll periods, billing cycles, or subscription renewals

Fill in form fields that require 'time employed' in years and months

Estimate travel itineraries where lodging is priced per business day