A method can be using find in conjunction with the tar command. First create a file with a timestamp to compare
touch -t 200710011500 /path/to/reftime
this will create an empty file (named reftime) with timestamp 01-Oct-2007 15:00. Then suppose you want to look for file newer than the above timestamp, and tar/gzip them
find /path/to/source/dir -cnewer /path/to/reftime -print0 | xargs -0 --no-recursion -zcvf /path/to/archive.tar.gz
Here I used the short form for tar options. The -cnewer option to the find command looks for files whose canghe time is more recent than the one of /path/to/reftime file. However this will include empty directories if (and only if) a directory has a timestamp newer than reftime and the files inside it are older, but in general this is not a common situation. I hope this helps a little.