files/en-us/web/javascript/reference/global_objects/date/sethours/index.md

metadata

title: Date.prototype.setHours()
short-title: setHours()
slug: Web/JavaScript/Reference/Global_Objects/Date/setHours
page-type: javascript-instance-method
browser-compat: javascript.builtins.Date.setHours
sidebar: jsref

The setHours() method of {{jsxref("Date")}} instances changes the hours, minutes, seconds, and/or milliseconds for this date according to local time.

{{InteractiveExample("JavaScript Demo: Date.prototype.setHours()")}}

const event = new Date("August 19, 1975 23:15:30");
event.setHours(20);

console.log(event);
// Expected output: "Tue Aug 19 1975 20:15:30 GMT+0200 (CEST)"
// Note: your timezone may vary

event.setHours(20, 21, 22);

console.log(event);
// Expected output: "Tue Aug 19 1975 20:21:22 GMT+0200 (CEST)"

Syntax

setHours(hoursValue)
setHours(hoursValue, minutesValue)
setHours(hoursValue, minutesValue, secondsValue)
setHours(hoursValue, minutesValue, secondsValue, msValue)

Parameters

• hoursValue
  • : An integer between 0 and 23 representing the hours.
• minutesValue {{optional_inline}}
  • : An integer between 0 and 59 representing the minutes.
• secondsValue {{optional_inline}}
  • : An integer between 0 and 59 representing the seconds. If you specify secondsValue, you must also specify minutesValue.
• msValue {{optional_inline}}
  • : An integer between 0 and 999 representing the milliseconds. If you specify msValue, you must also specify minutesValue and secondsValue.

Return value

Changes the {{jsxref("Date")}} object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description

If you do not specify the minutesValue, secondsValue, and msValue parameters, the same values as what are returned by {{jsxref("Date/getMinutes", "getMinutes()")}}, {{jsxref("Date/getSeconds", "getSeconds()")}}, and {{jsxref("Date/getMilliseconds", "getMilliseconds()")}} are used.

If a parameter you specify is outside of the expected range, other parameters and the date information in the {{jsxref("Date")}} object are updated accordingly. For example, if you specify 100 for secondsValue, the minutes are incremented by 1 (minutesValue + 1), and 40 is used for seconds.

Because setHours() operates on the local time, crossing a Daylight Saving Time (DST) boundary may result in a different elapsed time than expected. For example, if setting the hours crosses a spring-forward transition (losing an hour), the difference in timestamps between the new and old date is one hour less than the nominal hour difference. Conversely, crossing a fall-back transition (gaining an hour) result in an extra hour. If you need to adjust the date by a fixed amount of time, consider using {{jsxref("Date/setUTCHours", "setUTCHours()")}} or {{jsxref("Date/setTime", "setTime()")}}.

If the new local time falls within an offset transition, the exact time is derived using the same behavior as Temporal's disambiguation: "compatible" option. That is, if the local time corresponds to two instants, the earlier one is chosen; if the local time does not exist (there is a gap), we go forward by the gap duration.

Examples

Using setHours()

const theBigDay = new Date();
theBigDay.setHours(7);

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{jsxref("Date.prototype.getHours()")}}
• {{jsxref("Date.prototype.setUTCHours()")}}