[R] as.Date() clarification

Peter Dalgaard P.Dalgaard at biostat.ku.dk
Thu Jul 3 12:07:41 CEST 2008

Ron Michael wrote:
> When I use the code as.Date(0) the I get : "1970-01-01". My question is why it is like that? help file on as.Date seems to give no light on that. Can anyone clarify me?
Which version of R is this?

R version 2.7.1 (2008-06-23)
> as.Date(0)
Error in as.Date.numeric(0) : 'origin' must be supplied

and the help page has the explanation.

Internally, Date objects are represented as days since 1970-01-01, and
you can still exploit that with

> structure(0,class="Date")
[1] "1970-01-01"

although you really shouldn't need to have and shouldn't have to use
that knowledge.

[By the way, there used to be a way to see the current help pages on the
web, but I can't remember how. Searching for as.Date via the R search
sites doesn't  help either (interesting set of sponsored links from
Google though...), and the Wiki interface to help pages appears to be
> Regards,
> Send instant messages to your online friends http://uk.messenger.yahoo.com 
> 	[[alternative HTML version deleted]]

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