Gets the era, as defined by the chronology.
!(p)
The era is, conceptually, the largest division of the time-line.
Most calendar systems have a single epoch dividing the time-line into two eras.
However, some have multiple eras, such as one for the reign of each leader.
The exact meaning is determined by the {@code Chronology}.
!(p)
All correctly implemented {@code Era} classes are singletons, thus it
is valid code to write {@code date.getEra() == SomeChrono.ERA_NAME)}.
!(p)
This implementation uses {@link Chronology#eraOf(int)}.
@return the chronology specific era constant applicable at this date, not null
Gets the era, as defined by the chronology. !(p) The era is, conceptually, the largest division of the time-line. Most calendar systems have a single epoch dividing the time-line into two eras. However, some have multiple eras, such as one for the reign of each leader. The exact meaning is determined by the {@code Chronology}. !(p) All correctly implemented {@code Era} classes are singletons, thus it is valid code to write {@code date.getEra() == SomeChrono.ERA_NAME)}. !(p) This implementation uses {@link Chronology#eraOf(int)}.
@return the chronology specific era constant applicable at this date, not null