How to convert date to datetime to seconds since UNIX epoch in R with lubridate?

Question

I'm noticing this very confusing behavior.

library(lubridate)
x = as_date(-25567)
as.integer(as_datetime(x)) # Returns NA

How can I get this to return the seconds since (or in this case before) UNIX epoch?

Answer 1

This works with base R, now that we covered that you really want as.Date("1970-01-01") .

R> as.POSIXct("1900-01-01 00:00:00")    
[1] "1900-01-01 CST"                       
R> as.numeric(as.POSIXct("1900-01-01 00:00:00"))
[1] -2208967200        
R> 

I vaguely recall some OS-level irritations for dates prior to the epoch. This may fail for you on the world's most commonly used OS but that is not really R's fault...