Years Between Two Dates Calculator

Enter a start date and an end date to get the exact duration in years, months, and days, plus total days, weeks, and decimal years.

Quick Facts

Method
Calendar-accurate years/months/days breakdown
Counts full years, then full months, then remaining days — the same way you'd count by hand.
Average year
365.2425 days
Used to convert total days into decimal years, averaging in leap years over the Gregorian calendar's 400-year cycle.

Your Results

Calculated
Exact duration
-
Calendar years, months, and days
Total days
-
Full days between the dates
Total weeks
-
Total days ÷ 7
Total years (decimal)
-
Total days ÷ 365.2425

Ready

Enter a start date and an end date, then press Calculate.

How the Years Between Two Dates Calculator works

This tool measures the elapsed time between a start date and an end date two ways: a calendar-accurate breakdown into years, months, and days, and three running totals — total days, total weeks, and total years as a decimal. Both come from the same underlying day count, so they always agree with each other once you account for rounding.

The calendar breakdown (years, months, days)

The calculator counts the number of full years between the two dates, then the number of full months remaining after the last "anniversary," then whatever days are left over. This is the same method you would use counting on your fingers: from May 15, 1990 to August 10, 2026 is 36 full years (to May 15, 2026), plus 2 full months (to July 15, 2026), plus 26 remaining days — 36 years, 2 months, 26 days. When the end day of the month is earlier than the start day, the calculator borrows a month and uses that month's actual length (28, 29, 30, or 31 days), so leap years and short months are handled correctly.

Total days, weeks, and decimal years

  • Total days is the exact count of calendar days between the two dates.
  • Total weeks is total days divided by 7, shown to one decimal place.
  • Total years (decimal) is total days divided by 365.2425 — the average length of a year on the Gregorian calendar, which averages in the extra day added in leap years (roughly every 4th year, except century years not divisible by 400). Because it uses an average, this figure will differ slightly from the whole-number year count in the calendar breakdown.

Inclusive vs. exclusive counting

By default the calculator uses exclusive counting: the same elapsed-time method used for age (someone born on May 15, 1990 turns a year older on May 15, 1991, an exclusive one-year gap). Switching to inclusive counting adds one extra day so both the start date and end date are counted as whole days — this convention is common for rental periods, notice periods, and contract terms ("a 30-day notice period starting today" often means today counts as day one).

Common uses

  • Age and anniversary calculations
  • Project timelines and milestone planning
  • Contract terms, notice periods, and eligibility windows
  • Countdown and elapsed-time tracking for personal or historical dates

Precision note

This calculator uses whole calendar days and does not account for time zones or the exact hour of day. If your calculation has legal or contractual significance, confirm which counting convention (inclusive or exclusive) applies, since different jurisdictions and contract templates make different choices.

Frequently Asked Questions

How is the years, months, and days between two dates calculated?
The calculator counts full calendar years, then full calendar months from the last anniversary, then the remaining days, carrying across month and year boundaries the same way you would by hand. This calendar-accurate method correctly handles different month lengths and leap years, so it differs slightly from simply dividing total days by 365.
What is the difference between total days, total weeks, and total years?
Total days is the exact number of calendar days between the two dates. Total weeks divides that figure by 7. Total years (decimal) divides total days by 365.2425, the average length of a year on the Gregorian calendar once leap years are averaged in, so it will not exactly match the whole-number year count from the calendar breakdown.
What is the difference between inclusive and exclusive date counting?
Exclusive counting (the default) measures the elapsed time between the two calendar dates, the same way you would compute someone's age. Inclusive counting adds one extra day so that both the start date and the end date are counted as whole days in the total, which is common in contract terms, rental periods, and eligibility windows.

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