Did you upgrade your Perl installation without yet updating the non-core modules that you use? A current version of Perl wouldn't be binary compatible with an old module version. And vice versa: an old version of Perl wouldn't be binary compatible with new versions of modules.
This is not a DynaLoader issue. Reinstall a version of Date::Calc that matches the version of Perl you're using. The easiest way is to simply use the CPAN install tools to reinstall the modules that are giving you trouble. This will ensure that your current toolchain builds and compiles the modules, which will promote compatibility. The other way would be to make sure your ppm (package manager) is pointed to repositories that match the version of Perl you're using.
