[hadley]

I've never found that to be a problem in practice. Do you have an example where it's bitten you in practice?

(Also you should use UTC and not GMT)

[mapcar]

Hi Hadley, yes for instance

> as.chron("1970-01-01")+unclass(as.chron("2001-04-01")) [1] 04/01/01

> as.POSIXct("1970-01-01","EST")+unclass(as.POSIXct("2014-06-01","EST")) [1] "2014-06-01 05:00:00 EST"

If there is any conversion necessary it is difficult to get back the original intended time.

[hadley]

What does adding two dates together mean?

[mapcar]

Isn't this the conventional way of converting variables which have been coerced to their numeric representations back to time/date classes?