srt-shift is a simple command-line tool for shifting the times in a .srt subtitle file.
It worked on the two or three files I tried, but let me know if it doesn't work for you.
* To shift the subtitles backward 5 seconds:
srt-shift subtitles.srt -5
* To shift them forward 5 seconds:
srt-shift subtitles.srt 5
srt-shift will output the new subtitles to stdout, so to save them, do:
srt-shift subtitles.srt 5 > fixed.srt
That's all there is to it. You can find the latest version at < http://github.com/adeel/srt-shift >.