Change the year in a datetime object in R?

Question

I have the following:

\"0014-06-30\"

And I\'d like to change it to:

\"0000-06-30\"

How would I do this in

Answer 1

> x <- as.Date('0014-06-30')
> x
[1] "0014-06-30"
> library(lubridate)
> year(x)
[1] 14
> year(x) <- 0
> x
[1] "0000-06-30"

Answer 2

I couldn't get the specific format by converting to as.Date. A regex option would be

str1 <- "0014-06-30"
as.Date(str1)
#[1] "14-06-30"

sub('\\d{2}(?=-)', '00', str1, perl=TRUE)
#[1] "0000-06-30"

Answer 3

I would offer the following function to fix a mixed vector of two and four digit dates (where you have have formatted a string as a date if starting with a string):

library(lubridate)
two_dig_year_cnvt <- function(z, year=2017){
    y <- as.numeric(format(z, '%Y'))
    range <- 2017 - 2000
    year(z) <- ifelse(y >= 0 & y <= range, 2000 + y, 
                      ifelse(y > range & y <= 200, 1900 + y, y))
    z
}

This says for two digit years 00-16, assume that 2000 was the intended century, and for years 17-200 assume the century was 1900. Else, return the original year. If you're dealing with 19th century dates then of course this method is a no-go.