I had a movie and a subtitles file in srt format. The movie was a bit out of sync so I decided to write a simple python script to adjust the subtiles.
Works on Python 3.8+, does not have any dependencies.
python change_subtitle_timing.py --source_file source.srt --target_file target.srt --time_shift_seconds -0.8
the above example moves the timing of subtitles from the source.srt by -0.8 seconds (negative means that the subtitles will apear earlier) and puts the result in target.srt.