Gives a list of methods to get lesser (shorter) time units.
ie, for a month, this gives back ({"day"})
and the method day(mixed n) gives back that
day object. The method days() gives back a
list of possible argument values to the method day.
Concurrently, Array.map(o->days(),o->day) gives
a list of day objects in the object o.
Ie:
array(string) lesser() - gives back a list of possible xxx's.
object xxxs() - gives back a list of possible n's.
object xxx(mixed n) - gives back xxx n
object xxx(object(Xxx) o) - gives back the corresponing xxx
The list of n's (as returned from xxxs) are always in order.
There are two n's with special meaning, 0 and -1.
0 always gives the first xxx, equal to
my_obj->xxx(my_obj->xxxs()[0]), and -1 gives the last,
equal to my_obj->xxx(my_obj->xxxs()[-1]).
To get all xxxs in the object, do something like
Array.map(my_obj->xxxs(),my_obj->xxx).
xxx(object) may return zero, if there was no correspondning xxx.
Calendar_I._TimeUnit()->greater()