Used to build {@link GDate GDates}.
Like GDate, a GDateBuilder represents an Gregorian Date, Time, and Timezone, or subset of information (Year, Month, Day, Time, Timezone, or some combination). Wherever it provides guidance, the XML Schema 1.0 specification (plus published errata) is followed.
Instances may separately set or clear the year, month, day-of-month, and time-of-day. Not all operations are meaningful on all combinations. In particular, timezone normalization is only possible if there is a time, or a time together with a full date.