When attempting to log a Subversion repository you may get a "500 Internal Server Error" (via Apache), or "Could not access revision times" (via command line).
When svndumpfilter is used to filter revisions from a Subversion dump, the placeholder revisions have no date or time
To be able to do date ranged queries, you need the date to be set (as subversion does a binary search of revisions; hitting a null-dated revision breaks it)
The Subversion administrator (while a normal committer can do this, the pre-revprop-change script is managed on the server) must go through all revisions and set a date on them. The date needs to be set such that the revision ordering and date ordering is consistent.