# Calling this function causes the script to wait until the appropriate time
# e.g. wait_until "01:00 GMT" will make it wait until 1AM GMT
# Note that if the time is in the past it will just continue without waiting
function wait_until {
  current_epoch=$(date +%s)
  target_epoch=$(date -d "$1" +%s)
  sleep_seconds=$(( $target_epoch - $current_epoch ))
  if [ "$sleep_seconds" -gt "0" ]
    then
      sleep $sleep_seconds
  fi
}