Timestamp granularity is not an issue in the continuous model of time.
The adjective ``timestamp'' is used to distinguish this kind of
granularity from other kinds of granularity, such as the granularity
of non-timestamp attributes (+E9,+E1). ``Time granularity'' is
much too vague a term since there is a different granularity
associated with temporal constants, timestamps, physical clocks, and
the time-line clock although all these concepts are time-related.
Each time dimension has a separate timestamp granularity. A time,
stored in a database, must be stored in the timestamp granularity
regardless of the granularity of that time (e.g., the valid-time date
January 1st, 1990 stored in a database with a valid-time timestamp
granularity of a second must be stored as a particular second during
that day, perhaps midnight January 1st, 1990). If the context is
clear, the modifier ``timestamp'' may be omitted, for example,
``valid-time timestamp granularity'' is equivalent to ``valid-time
granularity'' (+E2).