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.''