A member of this class carries a value for a time, a date, an interval, a duration, or a collection of such values. Date and 24 hour time may be used separately or together, in which case the object carrying both values belongs is considered a timestamp. Two kinds of intervals are recognized, year-month intervals and day-time intervals. Date, time, timestamp, year-month interval and day-time interval are concepts borrowed from SQL. SAIF adds the notion of duration, which is defined by a starting point in time and an interval extending beyond that point. SAIF also separates the value for a time object from its temporal referencing, described below.