srt-shift is a simple command-line script 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.

Usage examples:

- 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

Installation:  sudo easy_install srt-shift

That's all there is to it.  You can find the latest version at
<http://github.com/adeel/srt-shift>.