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Date difference

Calculators

Calculate days, months and years between two dates.

Updated

Two dates

Add or subtract

Quick start

How to calculate the difference between two dates

Pick a From and To date, read the calendar diff plus raw totals — all in your browser.

  1. Step 1
    Pick two dates

    Use the date pickers to choose start and end. The tool defaults to today and 30 days out.

  2. Step 2
    Read calendar + totals

    Calendar diff (years / months / days) plus total days, weeks, business days, hours, minutes, seconds.

  3. Step 3
    Add or subtract

    Use the second panel to push a base date forward or back by years / months / days — useful for finding deadlines.

In-depth guide

Date difference calculator — calendar and raw totals

Calculate the difference between any two dates as calendar years/months/days, then see raw totals — days, weeks, business days, hours, minutes, seconds. Add or subtract years, months and days from a base date to find a future or past date.

Calendar diff vs raw totals

'2 years 3 months 14 days' is what you'd say in conversation. '839 days' is what a spreadsheet computes. Both are correct — they answer different questions.

  • Calendar diff respects variable-length months and leap years. Useful for age, tenure, lease term.
  • Total days ignores calendar structure. Useful for billing, SLA reporting, project planning.
  • Business days excludes Saturdays and Sundays. Note: doesn't account for holidays.

Typical use cases

  • Age in years/months/days for forms or legal docs.
  • Days remaining on a lease, subscription or warranty.
  • Project deadline ETA based on calendar working days.
  • Pregnancy or training-program week counting.
  • Time elapsed since an event ("it's been 47 days since…").

Edge cases worth knowing

  • Leap years — Feb 29 + 1 year clamps to Feb 28 the next non-leap year.
  • Month-end — Jan 31 + 1 month is Feb 28 / Feb 29, not Mar 3.
  • DST transitions — the day on which clocks change has 23 or 25 hours; total-hours figures account for this.
  • Direction — if your From is after your To, the calendar diff still shows magnitude. The 'direction' indicator notes which way you swapped.

Frequently asked questions

Does this tool send my dates anywhere?

No. All math runs in your browser using the JavaScript Date API. Works offline once the page is loaded.

How is the years/months/days breakdown computed?

Calendar-aware: we walk from the start date and increment years, then months, then days, borrowing days from the previous month when needed. That matches how people naturally count age and tenure.

What counts as a business day?

Monday through Friday in the from-date's local timezone. Holidays are not subtracted — they vary by country and would need a holidays library.

Why does total months / weeks show as a decimal?

Months are variable-length, so 'total months' is ambiguous — we don't show it. Total weeks is total days ÷ 7, which can produce a fraction. Total days is always an integer.

How does the 'add or subtract' panel handle Feb 29?

Adding one year to Feb 29 2024 lands on Feb 28 2025 — JavaScript's Date.setFullYear clamps to the last valid day of the month. Same for end-of-month additions (Jan 31 + 1 month = Feb 28/29).

Does it handle timezone?

Date pickers send local-date strings, and the math uses local midnight for each day, so the result reflects your timezone consistently.

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