JavaScript setFullYear(): Set or Change a Date Year

Date.prototype.setFullYear() changes the year of an existing Date in local time. It can also set the month and day in the same call, mutates the Date object, normalizes out-of-range values, and returns the updated timestamp.

Syntax:

date.setFullYear(year);
date.setFullYear(year, monthValue);
date.setFullYear(year, monthValue, dateValue);

A simple year change:

const date = new Date(2026, 8, 10);
date.setFullYear(2030);
console.log(date.getFullYear()); // 2030

Set only the year
Set year, month and day together
Add or subtract years
Leap-day behavior
Month/day overflow
Return value and mutation
UTC version
setYear() vs setFullYear()
Common mistakes

Setting Only the Year Top ↑

When only the year is supplied, the current month, day and time components remain in place where possible.

const date = new Date(2026, 3, 5, 9, 30);
date.setFullYear(2015);
console.log(date.toString());

Setting Year, Month and Day Together Top ↑

The optional second and third arguments use the same rules as the numeric Date constructor: months are zero-based and the day is the day of the month.

const date = new Date();
date.setFullYear(2028, 1, 29); // 29 Feb 2028
console.log(date.toDateString());

Adding or Subtracting Years Top ↑

Read the current year with getFullYear(), then set the adjusted year.

const date = new Date();
date.setFullYear(date.getFullYear() + 10);
console.log(date);

What Happens to February 29? Top ↑

Be careful when adding years to a leap-day date. If the target year does not have February 29, JavaScript normalizes the result into March.

const leapDay = new Date(2028, 1, 29);
leapDay.setFullYear(2029);
console.log(leapDay.toDateString()); // Thu Mar 01 2029

If your business rule means “last valid day of February,” detect and clamp that case explicitly.

Overflow in Month and Day Arguments Top ↑

Optional month/day values are normalized. Month 12 becomes January of the next year; day 0 means the final day of the previous month.

const date = new Date(2026, 0, 15);
date.setFullYear(2026, 12, 1);
console.log(date.toDateString()); // Fri Jan 01 2027

Return Value and Mutation Top ↑

const date = new Date();
const timestamp = date.setFullYear(2035);
console.log(typeof timestamp); // "number"
console.log(date.getFullYear()); // 2035

Using setUTCFullYear() Top ↑

setFullYear() interprets the components in local time. Use setUTCFullYear() when your calculation is defined in UTC.

const date = new Date("2026-12-31T23:30:00Z");
date.setUTCFullYear(2030);
console.log(date.toISOString());

setYear() vs setFullYear() Top ↑

Use setFullYear() for modern code. The older setYear() method has legacy handling for years 0–99 and should not be used for new work.

Common setFullYear() Mistakes Top ↑

Forgetting that optional months are zero-based.
Assuming February 29 remains February 29 in a non-leap target year.
Expecting a new Date rather than mutation.
Using local setters when the requirement is explicitly UTC.

Next: setHours() Date Reference

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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