The inLeapYear accessor property of Temporal.PlainYearMonth instances returns a boolean indicating whether this year-month is in a leap year. A leap year is a year that has more days (due to a leap day or leap month) than a common year. It is calendar-dependent.
The set accessor of inLeapYear is undefined. You cannot change this property directly.
For general information and more examples, see Temporal.PlainDate.prototype.inLeapYear.
const ym = Temporal.PlainYearMonth.from("2021-07");
console.log(ym.inLeapYear); // false
console.log(ym.daysInYear); // 365
console.log(ym.monthsInYear); // 12Temporal.PlainYearMonthTemporal.PlainYearMonth.prototype.with()Temporal.PlainYearMonth.prototype.add()Temporal.PlainYearMonth.prototype.subtract()Temporal.PlainYearMonth.prototype.yearTemporal.PlainYearMonth.prototype.daysInYearTemporal.PlainYearMonth.prototype.monthsInYearTemporal.PlainDate.prototype.inLeapYear