Toolivaro

Free Date Difference Calculator

Calculate the exact number of days, weeks, months, and years between two dates — with a single trusted method.

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How is the result calculated?

Contract period: Jan 15 to Apr 15

A contract runs from January 15 to April 15 of a non-leap year. The day count is 90 calendar days — that is 12 full weeks and 6 remaining days, 2 whole months, and 0 whole years. All four answers come from the same 90-day count, so they are internally consistent.

Input Value
startDate 2026-01-15
endDate 2026-04-15
Result 90 days · 12 weeks + 6 days · 2 months · 0 years

What is the formula and its assumptions?

Calendar days

days = |dateB − dateA| in calendar days

Symbol Meaning
dateA, dateB the two dates, order-independent
calendar days each midnight boundary counts as one day

Calendar days, not business days — weekends and holidays are included. Use the business-days calculator when they should not be.

Larger units (approximations)

weeks = ⌊days/7⌋ · months = ⌊days/30.44⌋ · years = ⌊days/365.25⌋

Symbol Meaning
⌊x⌋ floor — the largest whole unit that fits
30.44 average days per month
365.25 average days per year (leap years included)

What are the most common mistakes?

  • Counting both endpoints ("inclusive" math), which inflates day counts by one — the calculator uses midnight boundaries.
  • Mixing "weeks" and "business days" — this tool counts calendar days; business days are a separate tool.
  • Letting time-zone differences change a deadline count — calendar dates are time-zone independent.

What are the assumptions and limitations?

  • Month and year figures are averages, not calendar-aware (for example "2 months" is not tied to specific month lengths).
  • Calendar days include weekends and holidays by design.
  • The calculator works with dates only; time-of-day precision is out of scope.

Where do the numbers come from?

Last reviewed August 4, 2026 · Version 1.0.0 · Toolivaro does not guarantee external content.

Time Business Days Calculator Count business days between dates or add business days to a date — weekends and your own holidays excluded. Time Meeting Overlap Planner Find the time windows when teams in different time zones can meet, using their local work hours and DST-aware math. Time Time Zone Converter Convert any date and time between IANA time zones with correct daylight-saving handling and explicit offsets.

Frequently asked questions

Is the end date included in the count?

The calculator counts midnights between the two dates, so "January 1 to January 2" is 1 day and "January 1 to January 1" is 0 days. If your convention counts both endpoints, add one day to the result.

Why are months and years approximate?

Calendar months and years vary in length, so any month/year count is a convention. This calculator derives them from the exact day count with the standard averages (30.44 and 365.25) — consistent and defensible, and always agreeing with the day count on the same line.

Do time zones affect the result?

No — the calculator compares calendar dates, not instants. Two dates are the same pair of days everywhere on Earth, so daylight-saving changes cannot shift the day count.

Found a mistake or have a correction? Report it — we review every correction.