To start most date functions are dependant on NLS settings.
to properly debug this I will need to know the version of DBD::Oracle you are using as well I need some test code that will recreate it.
Nothing fancy is needed just a simple schema with some perl code that recreats the problem
By they way noone but me actully look at this list
You would be much better off posting this at
http://www.nntp.perl.org/group/perl.dbi.users/
or raise a RT ticket at
http://rt.cpan.org/Dist/Display.html?Queue=DBD-Oracle