library(zoo)
library(chron)

fmt = "%m/%d/%Y %H:%M"
tail1 = function(x) tail(x, 1)

test = read.zoo("http://dl.dropbox.com/u/41922443/test.txt",
   header = FALSE,
   FUN = function(idx) as.POSIXlt(idx, tz = "PDT", fmt),
   colClasses = rep(c(NA, "numeric", "NULL"), c(1, 1, 0)),
   sep = "\t", aggregate = tail1)