Date.prototype.toISOString()
Returns the date as an ISO 8601 string in UTC.
Syntax
date.toISOString()
Returns
string — A string like `YYYY-MM-DDTHH:mm:ss.sssZ` in UTC.
Throws
RangeError— The date is invalid.
Examples
const d = new Date(0);
console.log(d.toISOString());
Output
1970-01-01T00:00:00.000Z
const d = new Date("2026-05-15T12:30:00Z");
console.log(d.toISOString());
Output
2026-05-15T12:30:00.000Z
Notes
- Always expressed in UTC; the trailing `Z` denotes zero offset.
- This is the format `JSON.stringify()` uses for dates.
- The inverse is `new Date(isoString)` or `Date.parse()`.
Browser & runtime support
| Environment | Since version |
|---|---|
| chrome | 5 |
| firefox | 3.5 |
| safari | 4 |
| edge | 12 |
| node | 0.10 |