Years Between Dates Calculator
Enter a start date and an end date to instantly get the number of years between them — including the decimal fraction, whole years, remaining months, total weeks, and total days.
mo
d
mo
d
Exact years including the partial year fraction
- 1
Total calendar days
12,784Absolute difference between the two dates - 2
Years (÷ 365.25)
12,784 ÷ 365.25 = 35365.25 is the Gregorian average accounting for one leap day every four years
How does this calculator work?
Subtracts start date from end date to get total days, then divides by 365.25 for years (Gregorian average, leap-year-aware) and by 30.4375 for remaining months. Works for any past or future date range and doubles as an age calculator — enter your birth date and today to get your exact age.
Formula
How this is calculated
The calculator converts both dates to an internal timestamp, subtracts them, and divides by 86,400,000 (milliseconds per day) to get the exact day count. Dividing by 365.25 — the Gregorian four-year average that accounts for one leap year every four years — converts that to years as a decimal.
Whole years are extracted with a floor operation. The leftover days are then divided by 30.4375 (one-twelfth of 365.25) to estimate the remaining full months. Total weeks are shown alongside the raw day count for convenience.
If the end date is before the start date the absolute difference is returned with a note. All dates use the proleptic Gregorian calendar — historic dates before 1582 are handled consistently without applying the older Julian calendar correction.
Frequently asked questions
Enter your birth date as the start date and today (or any target date) as the end date. The result is your age in years, including the fractional partial year, whole years, and leftover months.
The Gregorian calendar adds a leap day every four years, making the long-run average 365.25 days. Using 365 would overcount or undercount by one day every four years across multi-year spans.
Year inputs go down to 1 CE. The proleptic Gregorian calendar is applied consistently, so the results are mathematically correct but may differ from historical calendar systems used before 1582.
Also known as
TG we-Calculate Editorial Team. (2026). Years Between Dates Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/years-between-dates-calculator
TG we-Calculate Editorial Team. "Years Between Dates Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/years-between-dates-calculator.
TG we-Calculate Editorial Team, "Years Between Dates Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/years-between-dates-calculator
@misc{wecalculate_years_between_dates_calculator, title = {Years Between Dates Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/years-between-dates-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?