Temporal.ZonedDateTime.prototype.day

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The day accessor property of Temporal.ZonedDateTime instances returns a positive integer representing the 1-based day index in the month of this date, which is the same day number you would see on a calendar. It is calendar-dependent.

The set accessor of day is undefined. You cannot change this property directly. Use the with() method to create a new Temporal.ZonedDateTime object with the desired new value.

For general information and more examples, see Temporal.PlainDate.prototype.day.

For PlainDate, day can only be non-continuous if the calendar skips days. For ZonedDateTime, day can also be non-continuous if the time zone changes its offset by 24 hours; this actually happened. See the example below.

Examples

Using day

js
const dt = Temporal.ZonedDateTime.from("2021-07-01[America/New_York]"); // ISO 8601 calendar
console.log(dt.day); // 1

Non-continuous day

To better align times with its trading partners in Asia, the country of Samoa changed its time zone to the other side of the International Date Line, shifting its offset from -10:00 to +14:00 (daylight saving time). This resulted in a 24-hour abrupt change in the local time, therefore skipping the day December 30, 2011 entirely. 2011-12-29T23:59:59-10:00[Pacific/Apia] is immediately followed by 2011-12-31T00:00:00+14:00[Pacific/Apia].

js
const dt = Temporal.ZonedDateTime.from(
  "2011-12-29T23:59:59-10:00[Pacific/Apia]",
);
console.log(dt.day); // 29
const nextDay = dt.add({ seconds: 1 });
console.log(nextDay.day); // 31

For this reason, you should always prefer add() and subtract() to manipulate dates and times, rather than directly changing the day property.

Specifications

Specification
Temporal proposal
# sec-get-temporal.zoneddatetime.prototype.day

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
day
Experimental

Legend

Tip: you can click/tap on a cell for more information.

No support
No support
Experimental. Expect behavior to change in the future.
See implementation notes.
User must explicitly enable this feature.

See also