as.IDate ignores origin

[DavidArenburg]

Searched for this in the issues but couldn't find it. It seem like as.IDate ignores origin

library(data.table) #v1.11.2
as.IDate(1000, origin = "1930-01-01")
## [1] "1972-09-27"
as.Date(1000, origin = "1930-01-01")
## [1] "1932-09-27"

[DavidArenburg]

I've took a look in the source code and I don't see any attention to origin in as.IDate.numeric. I think we could make a small change using something like

as.IDate.numeric <- function(x, origin = "1970-01-01", ...) as.IDate(origin, ...) + x
as.IDate(1000)
## [1] "1972-09-27"
as.IDate(1000, origin = "1930-01-01")
## [1] "1932-09-27"

This also won't brake compatibility with the old behavior

[tdeenes]

Found the same bug today. @DavidArenburg , have you considered submitting a PR for this?