In what format are CCK dates stored? If it stores dates in the database using a timestamp string instead of a native MySQL datetime format, what implications does that have in regards to storing dates before the unix epoch? Would it mean that CCK date fields would not be able to store something happening in year 1939, for example?
Date module provides three different formats, read about them here: Difference between date, datetime, and datestamp
Answering my last question based on @tim.plunkett links:
Would it mean that CCK date fields would not be able to store something happening in year 1939, for example?
It would depend on what format you chose for the storing the data of the CCK field. If you use Datestamp (Unix Timestamp), then no, you won't be able to store dates before the Unix epoch. If you need to do that, go for Date (ISO Date), or better Datetime, which represents stores data in MySQL's native date format, and allows to store dates before the Unix epoch.