SRT is a text file with a awk-able format that you can just write a script to update all the timestamps of. There's also a bunch of online services that do it. VLC has it built-in (track synchronisation - you can set delays on video audio and subtitle tracks individually).
porridgeraisin|2 years ago
kebsup|2 years ago
justinclift|2 years ago
At least, that's in the common Open Source video players such as vlc, mpv, mplayer, etc.