I think this is a problem with difftime (which gets called when the subtraction in your example is invoked). The first few lines of difftime are:
function (time1, time2, tz = "", units = c("auto", "secs", "mins", "hours", "days", "weeks")) { time1 <- as.POSIXct(time1, tz = tz) time2 <- as.POSIXct(time2, tz = tz) so any POSIXlt timezone gets clobbered with difftime's tz. Vadim Ogranovich <vograno <at> evafunds.com> writes: : : Hi, : : I have two data sources. One records time in PST time zone, the other in : GMT. I want to compute the difference between the two, but don't see : how. Here is an example where I compute time difference between : identical times each (meant to be) relative to its time zone. : : > as.POSIXlt("2000-05-10 10:15:00", "PST") - as.POSIXlt("2000-05-10 : 10:15:00", "GMT") : Time difference of 0 secs : : I was expecting to see 8hrs (which is the time difference between London : and San-Francisco). Why is it so and what is the correct way of doing : it? : : I use R-1.8.1 on RH-7.3. : : Thanks, : Vadim : : : [[alternative HTML version deleted]] : : ______________________________________________ : R-help <at> stat.math.ethz.ch mailing list : https://www.stat.math.ethz.ch/mailman/listinfo/r-help : PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html : : ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html