This feature is not Baseline because it does not work in some of the most widely-used browsers.
The daysInMonth accessor property of Temporal.PlainDateTime instances returns a positive integer representing the number of days in the month of this date. It is calendar-dependent.
The set accessor of daysInMonth is undefined. You cannot change this property directly.
For general information and more examples, see Temporal.PlainDate.prototype.daysInMonth.
const dt = Temporal.PlainDateTime.from("2021-07-01");
console.log(dt.daysInMonth); // 31
| Desktop | Mobile | Server | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | Bun | Deno | Node.js | |
daysInMonth |
144 | 144 | 139 | No | No | 144 | 139 | No | No | No | 144 | No | ? | 1.40 | No |
Temporal.PlainDateTimeTemporal.PlainDateTime.prototype.with()Temporal.PlainDateTime.prototype.add()Temporal.PlainDateTime.prototype.subtract()Temporal.PlainDateTime.prototype.yearTemporal.PlainDateTime.prototype.monthTemporal.PlainDateTime.prototype.dayTemporal.PlainDateTime.prototype.daysInWeekTemporal.PlainDateTime.prototype.daysInYearTemporal.PlainDate.prototype.daysInMonth
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal/PlainDateTime/daysInMonth