This should work:
sed 's%[0-9][0-9]\([0-9][0-9]\)/\([0-9][0-9]\)/\([0-9][0-9]\)%\1\2\3%' infile
- You can change sed's separator (/) to anything you like, I used %. This to avoid escaping the / in the date string.
- Sed can use backreferencing. I.e. something in the searchstring surrounded by () (need to be escaped) can be represented by \1 (\2 \3 etc) in the replace string.
Take a look here
(it's about halfway down the article) for another sed backreference explanation/example.
The same can be done for the time string, but that's for you to figure out
If anything is unclear or you cannot get it to work: Just ask.