If add a new option, I prefer to add it to the ZipFile constructor, similarly to allowZip64. Initially allowZip64 was False by default, because not all third-party tools supported ZIP64 extension. Later the default was changed to True, but you still can force raising an error if the archive is not compatible with old tools. I think the same policy should be applied here. Add the ability of writing date before 1980, and add an option for raising an error for date before 1980.