An S4 class to represent a Julian calendar.
See also
Other classes:
AD-class,
BC-class,
BCE-class,
BP-class,
CE-class,
GregorianCalendar-class,
RataDie-class,
TimeScale-class,
TimeSeries-class,
b2k-class
Other calendar classes:
GregorianCalendar-class,
TimeScale-class