The solution you've mentioned could be used if you first get the list of all files in the repository and then apply the solution for every of them. It would be very slow though if you have many files in the repo.
Faster option could be to fetch the whole svn log of the repo and analyze the output.
svn log <repo_URL> --verbose -r 1:HEAD
svn log
will provide info about revisions along with theirs date.
--verbose
option will give you info about added files for every revision.
------------------------------------------------------------------------
r31 | harry | 2003-01-10 12:25:08 -0600 (Fri, 10 Jan 2003) | 1 line
Changed paths:
A /trunk/src/bar.c
Added new file bar.c
This way you may collect the info you need relatively fast. Option --xml
could be useful for you if you can easily parse xml - this way svn log
output will be clearly structured and perhaps easier to parse.