# Deal with timestamps using the date command
function timestamp  --wraps "date" --description "Return current unix timestamp"
  # Without argument it only prints the current timestamp
  if test (count $argv) -gt 0
    # If the argument if help or --help or -h, it prints usage.
    if test "$argv[1]" = "--help" -o "$argv[1]" = "-h" -o "$argv[1]" = "help"
      echo -e "timestamp [TIMESTAMP]\n"
      echo "Print the current timestamp"
      echo "Pass a timestamp to get the corresponding date, so timestamp (timestamp) = date."
    else
      # Convert the argument to ISO 8601 date
      date --iso-8601=seconds -d @$argv[1]
    end
  else
    # The Unix timestamp is the number of seconds from 01 January 1970 (the unix epoch date)
    date "+%s"
  end
end