A month-day _in the ISO-8601 calendar system, such as {@code --12-03}. !(p) {@code MonthDay} is an immutable date-time object that represents the combination of a month and day-of-month. Any field that can be derived from a month and day, such as quarter-of-year, can be obtained. !(p) This class does not store or represent a year, time or time-zone. For example, the value "December 3rd" can be stored _in a {@code MonthDay}. !(p) Since a {@code MonthDay} does not possess a year, the leap day of February 29th is considered valid. !(p) This class implements {@link TemporalAccessor} rather than {@link Temporal}. This is because it is not possible to define whether February 29th is valid or not without external information, preventing the implementation of plus/minus. Related to this, {@code MonthDay} only provides access to query and set the fields {@code MONTH_OF_YEAR} and {@code DAY_OF_MONTH}. !(p) The ISO-8601 calendar system is the modern civil calendar system used today _in most of the world. It is equivalent to the proleptic Gregorian calendar system, _in which today's rules for leap years are applied for all time. For most applications written today, the ISO-8601 rules are entirely suitable. However, any application that makes use of historical dates, and requires them to be accurate will find the ISO-8601 approach unsuitable.