The basic components of all DateTime and Interval data types are components called DateTime fields. All DateTime fields are represented internally as logical records of integer numbers, though the values are defined as type DateTime, not NUMERIC.
DateTime and Interval Data and Character Data Types
Because Unicode is supported, references to all character data lengths and format lengths should be interpreted as logical lengths and not as the number of bytes.
DateTime data exported to host processes are handled as character data. The physical size of values depends on the host character set.