javascript format date as YYYY-MM-DD

For a YYYY-MM-DD string in UTC, use date.toISOString().slice(0, 10). For the local date (what the user's clock shows), build it from the parts: `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}-${String(d.getDate()).padStart(2, "0")}`, or let Intl.DateTimeFormat with the en-CA locale or formatToParts do it for a chosen time zone. The two can differ by a day around midnight.

UTC, local and a specific time zone

The example sets process.env.TZ at the top of the script (Node.js honours it at run time) so the output is the same on every machine; in real code the local time zone comes from the system.

cat > date.mjs <<'EOF'
process.env.TZ = "Europe/Rome"; // pin the local zone for this example
const d = new Date("2026-03-01T23:30:00Z"); // 23:30 UTC on 1 March

console.log("UTC (toISOString):", d.toISOString().slice(0, 10));

const pad = (n) => String(n).padStart(2, "0");
const local = `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`;
console.log("local parts:     ", local, `(TZ=${process.env.TZ})`);

const tokyo = new Intl.DateTimeFormat("en-CA", { timeZone: "Asia/Tokyo" }).format(d);
console.log("en-CA in Tokyo:  ", tokyo);

const parts = Object.fromEntries(
  new Intl.DateTimeFormat("en-US", { timeZone: "America/New_York", year: "numeric", month: "2-digit", day: "2-digit" })
    .formatToParts(d)
    .map((p) => [p.type, p.value]),
);
console.log("parts in New York:", `${parts.year}-${parts.month}-${parts.day}`);

try {
  new Date("31/12/2026").toISOString();
} catch (e) {
  console.log(`${e.name}: ${e.message}`);
}
EOF
node date.mjs

UTC (toISOString): 2026-03-01
local parts:      2026-03-02 (TZ=Europe/Rome)
en-CA in Tokyo:   2026-03-02
parts in New York: 2026-03-01
RangeError: Invalid time value

At 23:30 UTC it is already 2 March in Rome and Tokyo, but still 1 March in UTC and New York. That is the classic "off by one day" bug: toISOString() is always UTC.

Options

Pitfalls

• Parsing a date-only string. new Date("2026-03-01") is read as midnight UTC, while new Date("2026-03-01T00:00") is midnight local time. Formatting the first with local getters west of UTC prints the previous day.
• Locale patterns can change. en-CA and sv-SE happen to format as YYYY-MM-DD; formatToParts does not depend on any locale's pattern and is the safer choice for machine-readable output.
• Invalid dates. toISOString() throws RangeError: Invalid time value on an invalid Date; the local getters return NaN, which prints as NaN-NaN-NaN.
• Missing values. Calling .toISOString() on undefined throws Cannot read properties of undefined.

Confirm it worked

Test with a time close to midnight, as above, and in at least two time zones (TZ=America/New_York node app.js on Linux and macOS). If both print the date you expect, the formatting handles time zones correctly.

FAQ