R Date Timestamp Epoch Unix Time

timestamps_in_R.R

library(lubridate)  #   <3 tidyverse


# this is likely not the most efficient way to generate unix time stamps, but it is intuitive to me
# I like to see how it is done step by step
# to make this more efficient, you could store  the "epoch" value outside the function so it
# doesn't have to be calculated every time you call the function
time_since_epoch <- function() {
  x1 <- as.POSIXct(Sys.time())
  x2 <- format(x1, tz="GMT", usetz=F)
  x3 <- lubridate::ymd_hms(x2)
  epoch <- lubridate::ymd_hms('1970-01-01 00:00:00')
  time_since_epoch <- (x3 - epoch) / dseconds()
  return(time_since_epoch)
}




# helper timestamp function - generating timestamps that are compatible with Amazon's Product Advertising API
gen_utc_ts <- function(ts) {
  
  # x1: timestamp in current system timezone
  # x2: format with tz argument changes the timezone to GMT/UTC
  # x3: lubridate objects are easier to work with and manipulate
  x1 <- as.POSIXct(ts)
  x2 <- format(x1, tz = "GMT", usetz = F)
  x3 <- lubridate::ymd_hms(x2)
  
  # reformat the string manually (kinda sloppy, but lots of control)
  return(paste0(
    sprintf("%04d", lubridate::year(x3)),   '-', 
    sprintf("%02d", lubridate::month(x3)),  '-',
    sprintf("%02d", lubridate::day(x3)),    'T', 
    sprintf("%02d", lubridate::hour(x3)),   ':',
    sprintf("%02d", lubridate::minute(x3)), ':', 
    sprintf("%02d", lubridate::second(x3)), 'Z'))
}