toISOStringDate()

function toISOStringDate(this, isLocal?): string;

Defined in: date/iso-date.ts:31

Converts a Date object to an ISO 8601 date string (YYYY-MM-DD) By default, the Date is computed in UTC (i.e. based on Date.prototype.toISOString()), which means the returned value may differ from the local calendar day if your local timezone is behind/ahead of UTC.

If isLocal is set to true, the date is instead computed using local time (getFullYear(), getMonth(), getDate()), so the string always reflects the local calendar date.

Parameters

Parameter	Type	Default value	Description
this	Date	undefined	Date object instance
isLocal?	boolean	false	If true, uses local time; otherwise, uses UTC time

Returns

string

The ISO 8601 date string

Example

const d = new Date("2025-03-15T23:30:00Z");

// UTC-based date (default):
d.toISOStringDate();     // e.g. "2025-03-15"

// Local-time-based date:
d.toISOStringDate(true); // e.g. "2025-03-16" in a timezone ahead of UTC

Since

1.1.0

Author

Ian Wenneckers