moritz already mentioned command line sort...here's how to do it (if you are on windows( as jrsimmon believes), go get MSYS):

> # The file is tab delimited (your time field having spaces shouldn't
+ matter)
> cat tmp.txt
3       1a      2       b
2       2c      3       b
1       3b      1       b
> # The char between the quotes is a tab ("\t" works in ksh)
> sort -t" " -k3n tmp.txt
1       3b      1       b
3       1a      2       b
2       2c      3       b
>
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Update: I do not claim that the above quotes are properly escaped for Windows. Actually I'm not even sure how to escape them in the cmd shell, but this works from perl:

system('sort',"-t", "\t","-k3n","tmp.txt");
[download]