Friends don't let friends use new Date().
JavaScript's original Date object is a 1995 port of java.util.Date. It's mutable, confusing (months are 0-indexed, days are 1-indexed), and fails at basic arithmetic.
The Temporal API is the clean slate we've been waiting for: A robust, immutable, timezone-aware standard built for the modern web.
Why the `Date` object failed us
- Mutability:
date.setHours(0)modifies the object in place. This causes bugs when dates are shared across components. - 0-Indexed Months:
new Date(2023, 0, 1)is January.new Date(2023, 1, 1)is February. This off-by-one error has wasted millions of developer hours. - Parsing Inconsistency: Browser support for parsing strings like
"2023-01-01"varies dangerously between UTC and Local time.
02. Immutable & Type-Safe
Clear Benefits
Temporal handles concepts distinctively: Wall-Clock time (PlainDate) vs. Absolute time (Instant) vs. Zoned time (ZonedDateTime). This prevents you from accidentally mixing up "local time" with "UTC time".
Temporal.PlainDate
// Just a calendar date. No time. No timezone.
const birthday = Temporal.PlainDate.from('2026-05-15');
Temporal.ZonedDateTime
// Complete precision.
const meeting = Temporal.Now.zonedDateTimeISO('Asia/Tokyo');
03. Time Zone Sanity & Arithmetic
Time zones and Daylight Saving Time (DST) are notorious sources of bugs in date and time handling. The native Date object offers minimal help, often requiring complex external libraries to manage these intricacies. Temporal, however, was built from the ground up with time zones in mind, making operations like adding hours across DST boundaries or comparing dates in different zones straightforward and reliable.
Temporal.ZonedDateTime is your go-to for representing a specific moment in time within a particular time zone. It automatically handles offsets, DST transitions, and provides robust methods for arithmetic and comparison.
Adding Time (DST Safe)
const flight = Temporal.ZonedDateTime.from(
'2026-03-14T10:00:00[America/New_York]'
); // Day before DST changes
// Add 24 hours (wall clock time)
const nextDay = flight.add({ hours: 24 });
// Temporal knows if 24 hours actually lands at 10am or 11am based on DST rules!
Comparing Dates
const d1 = Temporal.PlainDate.from('2026-01-01');
const d2 = Temporal.PlainDate.from('2026-06-01');
const duration = d1.until(d2);
console.log(duration.toString()); // "P5M" (Period: 5 Months)
console.log(d1.equals(d2)); // false
Sorting
const dates = [
Temporal.PlainDate.from('2026-01-01'),
Temporal.PlainDate.from('2025-12-31')
];
dates.sort(Temporal.PlainDate.compare); // Built-in comparator!
05. Senior Guidance
Delete your libraries.
Moment.js is 300kb. Date-fns is lighter but still adds bundle weight.
Temporal is built-in. It costs 0kb. It's faster because it's C++ binding in V8.
The only reason to keep using libraries is if you need complex human-readable formatting like "3 minutes ago" (RelativeTimeFormat covers some of this) or legacy browser support without polyfills.