JavaScript Date

What You’ll Learn

Dates and times appear in almost every app — logs, bookings, countdowns, and APIs. This hub links to 46 Date method tutorials for reading parts, mutating values, formatting strings, and working in UTC.

Introduction

JavaScript provides a built-in Date object for working with moments in time. Unlike many languages, months are zero-based (0 = January), and the object is mutable — setters change the same instance.

What Are Date Methods?

Date methods fall into a few groups: getters read year, month, day, and clock fields; setters update them; formatters produce strings; and static helpers like Date.now() and Date.parse() work without an instance.

Local Time vs UTC

• Local — getHours(), setMonth() use the user’s timezone.
• UTC — getUTCHours(), setUTCDate() ignore local offset.
• Timestamp — getTime() and Date.now() return milliseconds since the epoch (timezone-agnostic).

📝 Syntax

Create and inspect a date:

const now = new Date();
const timestamp = Date.now();

console.log(now.getFullYear());   // local year
console.log(now.getUTCMonth());   // UTC month (0–11)
console.log(now.toISOString());   // "2026-07-17T10:30:00.000Z"

Method groups

When to Use Which Methods

• Now — Date.now() for performance timing or unique IDs.
• Parse user input — new Date(string) or Date.parse() (validate results — parsing is inconsistent for some formats).
• Display — toLocaleDateString() / toLocaleTimeString() for UI.
• APIs & databases — toISOString() for JSON payloads.
• Math across days — convert to timestamps with getTime(), add milliseconds, create new Date(ms).

Examples Gallery

Open DevTools Console (F12) and paste each snippet to see formatted date output.

const ms = Date.now();
const date = new Date(ms);

console.log("Timestamp:", ms);
console.log("ISO:", date.toISOString());

Timestamp: 1721212200000
ISO: 2026-07-17T10:30:00.000Z

const d = new Date(2026, 6, 17); // Jul 17, 2026 (month 6)

console.log("Year:", d.getFullYear());
console.log("Month index:", d.getMonth());   // 6 = July
console.log("Day:", d.getDate());

Year: 2026
Month index: 6
Day: 17

const currentDate = new Date();

console.log("Date:", currentDate.toDateString());
console.log("ISO:", currentDate.toISOString());

Date: Fri Jul 17 2026
ISO: 2026-07-17T10:30:00.000Z

const currentDate = new Date();

console.log("Time:", currentDate.toLocaleTimeString());
console.log(
  "Weekday:",
  currentDate.toLocaleDateString("en-US", { weekday: "long" })
);

Time: 4:00:00 PM
Weekday: Friday

const deadline = new Date(2026, 6, 28);
deadline.setDate(deadline.getDate() + 7);

console.log("One week later:", deadline.toDateString());

One week later: Mon Aug 04 2026

💬 Usage Tips

• Timezone awareness — document whether UI shows local or UTC; use UTC getters for server sync.
• Validate parsed dates — isNaN(date.getTime()) detects invalid Date objects.
• Prefer ISO in JSON — JSON.stringify calls toJSON() → ISO string.
• Avoid string parsing traps — new Date("2026-07-17") may parse as UTC midnight; test your format.
• Search this index — jump to any of 46 method pages above.

⚠️ Common Pitfalls

• Zero-based months — July is 6, not 7, in getters and the constructor.
• Mutable dates — setters change the original object; clone first if needed.
• Daylight saving jumps — local setHours() can skip or repeat hours on DST boundaries.
• Legacy Date.parse — implementation-dependent for non-ISO strings; prefer explicit parsing.
• Sort as strings — compare getTime() numbers, not formatted date strings.

💡 Best Practices