What this calculator does
This calculator answers years between two dates directly, leading with a single decimal figure rather than a mixed breakdown of years, months and weeks. Enter any two dates in either order and it returns the span as a precise number of years, alongside the whole-years-and-remainder version for when a rounder figure is more useful.
Years are not a fixed length any more than months are: a calendar year runs 365 or 366 days depending on leap years, so a plain years-between-two-dates count has to pick a convention. This calculator divides the total days by 365.2425, the average length of a year over the 400-year Gregorian cycle, which keeps the decimal figure accurate over both short and very long spans.
The formula
The total number of days between the two dates is divided by 365.2425 to give the decimal years figure. Separately, whole calendar years are counted forward from the earlier date to the later one, the way you would count birthdays, with whatever months and days are left over shown as the remainder.
| Term | Meaning |
|---|---|
| Decimal years | Total days between the dates divided by 365.2425, the average Gregorian year length. |
| Whole years | Complete calendar years counted forward from the earlier date, the same way age is counted. |
| Remainder | The months and days left over after the last whole year. |
The inputs explained
| Field | What to enter |
|---|---|
| First date | The earlier of the two dates, or either date; order does not matter. |
| Second date | The other date. If it falls before the first date, the calculator swaps them and calculates forward in time. |
When to use it
Reporting tenure or a length of service
A precise decimal such as 4.7 years is often what a form, contract or HR record actually wants, rather than a broken-down years-months-days sentence.
Comparing two long spans
Decimal years makes it easy to compare two multi-year periods directly, such as how a 6.2-year gap stacks up against an 8.9-year one, without converting a mixed breakdown in your head.
Confirming a round-number anniversary
The whole-years-and-remainder line shows exactly how many complete years have passed and how far into the next year the second date falls, which settles whether an anniversary has actually been reached.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the years-between figure grows as the end date moves further out
A fixed start date of 1 January 2020, against a range of later end dates.
| End date | Years between the dates | Whole years and remainder |
|---|---|---|
| 2021-01-01 | 1.00 years | 1 years, 0 months, 0 days |
| 2023-01-01 | 3.00 years | 3 years, 0 months, 0 days |
| 2025-01-01 | 5.00 years | 5 years, 0 months, 0 days |
| 2028-01-01 | 8.00 years | 8 years, 0 months, 0 days |
| 2030-01-01 | 10.00 years | 10 years, 0 months, 0 days |
| 2035-01-01 | 15.00 years | 15 years, 0 months, 0 days |
Short spans measured in years
A fixed start date, against end dates only a few months to a couple of years later.
| End date | Years between the dates | Total days between the dates |
|---|---|---|
| 2024-06-15 | 0.25 years | 92 |
| 2024-09-15 | 0.50 years | 184 |
| 2024-12-15 | 0.75 years | 275 |
| 2025-03-15 | 1.00 years | 365 |
| 2025-09-15 | 1.50 years | 549 |
| 2026-03-15 | 2.00 years | 730 |
Questions
Why 365.2425 instead of 365 or 365.25?
365.2425 is the average length of a year in the Gregorian calendar once its leap-year rule is fully accounted for (a leap year every 4 years, except century years not divisible by 400). It is more accurate than the simpler 365.25 approximation used by the Julian calendar.
Does the order I enter the dates in matter?
No. If the second date is earlier than the first, the calculator swaps them and works forward in time, so the result is always a positive span.
How is this different from the full years, months and days breakdown?
The time between dates calculator leads with the full years-months-days-and-more breakdown. This calculator leads with a single decimal years figure, for when that is the number you actually need.
Can the decimal years figure be used for age?
It works arithmetically, but for a person's exact age the how old am I calculator is built specifically for that, and reports the figure the way age is normally counted rather than as a raw decimal.
For the fuller years, months, weeks and days breakdown, see the time between dates calculator. For a months-first view of the same kind of span, use the months between two dates calculator.