Temporal.ZonedDateTime.prototype.day

The day accessor property of {{jsxref("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 {{jsxref("Temporal/ZonedDateTime/with", "with()")}} method to create a new Temporal.ZonedDateTime object with the desired new value.

For general information and more examples, see {{jsxref("Temporal/PlainDate/day", "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#

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].

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 {{jsxref("Temporal/ZonedDateTime/add", "add()")}} and {{jsxref("Temporal/ZonedDateTime/subtract", "subtract()")}} to manipulate dates and times, rather than directly changing the day property.

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("Temporal.ZonedDateTime")}}
• {{jsxref("Temporal/ZonedDateTime/with", "Temporal.ZonedDateTime.prototype.with()")}}
• {{jsxref("Temporal/ZonedDateTime/add", "Temporal.ZonedDateTime.prototype.add()")}}
• {{jsxref("Temporal/ZonedDateTime/subtract", "Temporal.ZonedDateTime.prototype.subtract()")}}
• {{jsxref("Temporal/ZonedDateTime/year", "Temporal.ZonedDateTime.prototype.year")}}
• {{jsxref("Temporal/ZonedDateTime/month", "Temporal.ZonedDateTime.prototype.month")}}
• {{jsxref("Temporal/ZonedDateTime/daysInMonth", "Temporal.ZonedDateTime.prototype.daysInMonth")}}
• {{jsxref("Temporal/ZonedDateTime/dayOfWeek", "Temporal.ZonedDateTime.prototype.dayOfWeek")}}
• {{jsxref("Temporal/ZonedDateTime/dayOfYear", "Temporal.ZonedDateTime.prototype.dayOfYear")}}
• {{jsxref("Temporal/PlainDate/day", "Temporal.PlainDate.prototype.day")}}