strftime
does the opposite. dt_str <- "May 4 2016" dummy <- Sys.setlocale(category = "LC_ALL", locale = "en_US.UTF-8") # # See ?strptime for a list of %-modifiers # dt_ <- strptime(dt_str, "%b %e %Y") class(dt_) # [1] "POSIXlt" "POSIXt" dt_ # [1] "2016-05-04 CEST"