The .Date and .Time "fields" are what we programmers like to call "Union" struct members of the individual fields.
As the Help topic explains, these are each a DWORD, which overlap the members of the words/bytes of the ACTUAL individual date/time fields.
The purpose? In case you needed to move just the TIME values or just the DATE values from this structure into another DWORD (or probably another TIME or DATE field in another Date/Time structure). Rather than having to do it in pieces parts, you can do it as just the .Date portion or just the .Time portion. It's definitely not a "critical" need, but for those who want to log just the Time or archive just the date, it provides a DWORD form of each of those (even Data View and Right-Click Format in online status Ladder parms supports this UNIONed form of a Date and Time, i.e. "Date Field" or "Date in Date/Time Struct")