Date.prototype.setMilliseconds() changes the milliseconds of a date in local time (typically 0–999). It mutates the Date in place and returns the new timestamp.
date.setMilliseconds(ms)
ms: usually 0 … 999 (local)
→ returns new timestamp (ms)
→ mutates date
setMilliseconds(456) // exact fraction
setMilliseconds(1005) // overflow → +1 second, ms = 5
getMilliseconds() → read twinCall date.setMilliseconds. Start with this line.
date.setMilliseconds(ms)| Call | What it does |
|---|---|
date.setMilliseconds(ms) | Primary signature. |
date.setMilliseconds(...) | Call with the arguments your case needs. |
Built into JavaScript. Call setMilliseconds(...) on a Date instance — no import required.
date.setMilliseconds(ms)| Parameter | Description |
|---|---|
| millisecondsValue | Required. Local milliseconds (typically 0–999; overflow allowed) |
| Return Value | Description |
|---|---|
| * | New epoch ms (number), not the Date |
Write a value in the normal 0–999 range.
const event = new Date(1975, 7, 19, 23, 15, 30);
console.log(event.getMilliseconds()); // 0
event.setMilliseconds(456);
console.log(event.getMilliseconds()); // 4560.getMilliseconds() confirms 0.456. setMilliseconds(456) updates only the fraction.getMilliseconds() now returns 456.Values above 999 roll into the seconds field.
const d = new Date(2026, 2, 15, 10, 0, 30, 0);
d.setMilliseconds(1005);
console.log(d.getSeconds()); // 31
console.log(d.getMilliseconds()); // 530, milliseconds 0.1005 = 1000 + 5 → add 1 second, keep 5 ms.31; milliseconds become 5.Clear the fraction so the timestamp lands on a whole second.
const d = new Date(2026, 2, 15, 10, 0, 30, 789);
d.setMilliseconds(0);
console.log(d.getMilliseconds()); // 0
console.log(d.getSeconds()); // 30789.setMilliseconds(0) writes zero.30.Date.prototype.setMilliseconds() has been in JavaScript since ES1. It is Baseline and works in every modern browser and Node.js — no polyfill needed.
Supported everywhere Date exists: Chrome, Firefox, Safari, Edge, Internet Explorer, and all Node.js versions.
Bottom line: Safe to use in any environment. Watch mutation and overflow into seconds. See also the MDN setMilliseconds() reference.
Learn how to set the minutes portion of a Date in local time.
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