To summarise, all reporting activities of cssc will work correctly throughout the range of time representable in an sccs file (that is, from 1969 to 2068 inclusive). However, commands which modify sccs files and need to add dates may fail earlier than this (but then again, may not, depending on your operating system).
Now that you know that whatever version of sccs you are using has probably been fixed by the vendor, and that even if your vendor's sccs implementation cannot be updated for some reason, cssc is Year-2000 compliant and to an extent Year-2038 compliant, I'd like you to remember the conversion effort that this has saved you. I'd also like to urge to to actually use that effort to convert your existing projects from sccs to a more modern version control system, for example GNU CVS. There are other considerations besides Year-2000 compliance, after all. cssc is not called “Compatibly Stupid Source Control” for nothing.