method Temporal.Calendar.prototype.dateAdddateAdd(date: Temporal.PlainDate | PlainDateLike | string,duration: Temporal.Duration | DurationLike | string,options?: ArithmeticOptions,): Temporal.PlainDateParametersdate: Temporal.PlainDate | PlainDateLike | stringduration: Temporal.Duration | DurationLike | stringoptionaloptions: ArithmeticOptionsReturnsTemporal.PlainDate