Set the creation timestamp of an MP4 file using `ffmpeg`

fftimestamp.sh

#!/usr/bin/env bash

set -euo pipefail

function main() {
  local input="$1"
  local output="$2"
  local timestamp="$3"

  if [[ "$input" == "$output" ]] ; then
    echo "input and output files must be different"
    exit 2
  fi
  echo ffmpeg -i "$input" -c copy -map_metadata 0 -metadata creation_time="$timestamp" "$output"
}

main "$@"