Date difference in years — diff

Calculate date difference in years, taking into account leap years.

Usage

diff_years(start, stop)

Arguments

start: starting date of time interval
stop: ending date of time interval

Value

A numeric value representing the date difference in years

Details

Since the number of days in a year changes depending on whether said year is a leap year, dividing a period of time by estimates such as 365.25, 365.241, 365.24442 will be slightly biased. The correct way to calculate a length of period in years is to take into account which years are leap years and divide by 365 or 366 as needed.

Examples

start <- as.Date("2009-03-08")
stop <- as.Date("2009-08-09")
diff_years(start, stop)
#> [1] 0.4219178