title: Date.prototype.setMilliseconds()
short-title: setMilliseconds()
slug: Web/JavaScript/Reference/Global_Objects/Date/setMilliseconds
page-type: javascript-instance-method
browser-compat: javascript.builtins.Date.setMilliseconds
sidebar: jsref
The setMilliseconds() method of {{jsxref("Date")}} instances changes the milliseconds for this date according to local time.
{{InteractiveExample("JavaScript Demo: Date.prototype.setMilliseconds()")}}
const event = new Date("August 19, 1975 23:15:30");
console.log(event.getMilliseconds());
// Expected output: 0
event.setMilliseconds(456);
console.log(event.getMilliseconds());
// Expected output: 456
Syntax
setMilliseconds(millisecondsValue)
Parameters
millisecondsValue- : An integer between 0 and 999 representing the milliseconds.
Return value
Changes the {{jsxref("Date")}} object in place, and returns its new timestamp. If millisecondsValue 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 specify a number outside the expected range, the date information in the {{jsxref("Date")}} object is updated accordingly. For example, if you specify 1005, the number of seconds is incremented by 1, and 5 is used for the milliseconds.
Because setMilliseconds() 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 milliseconds 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 time 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/setUTCMilliseconds", "setUTCMilliseconds()")}} 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 setMilliseconds()
const theBigDay = new Date();
theBigDay.setMilliseconds(100);
Specifications
{{Specifications}}
Browser compatibility
{{Compat}}
See also
- {{jsxref("Date.prototype.getMilliseconds()")}}
- {{jsxref("Date.prototype.setUTCMilliseconds()")}}