"None" does not change the date and time data in the cell. It tells the cell to not display the the time art of the date and time value.
ALL 'dates' and ALL 'times' in Pages tables and in Numbers tables are Date and Time values specifying a specific instant in time.
IF you enter only the date part, Pages or Numbers completes the entry by adding the time part as 00:00:00 (midnight at the beginning of that date).
If you enter only the time part, Pages or Numbers completes the date and time value by setting the date part to the date the entry was made.
You can format the cell to show onlt the date part or to show only the time part, but that changes only the format, and not the content of the cell.
Regards,
Barry