JavaScript Dates

What is a Date in JavaScript?

JavaScript uses the Date object to work with dates and times.

const now = new Date();
console.log(now); // Current date and time

Behind the scenes, JavaScript stores dates as the number of milliseconds since January 1, 1970 (Unix Epoch).

Creating Date Objects

You can create a Date in several ways:

1. Current Date and Time

const now = new Date();

2. Specific Date and Time

const birthday = new Date("2000-06-15");
const meeting = new Date("2025-04-30T10:30:00");

3. Using Individual Values

new Date(year, monthIndex, day, hours, minutes, seconds)

const customDate = new Date(2025, 3, 30, 10, 30); // April 30, 2025 (month is 0-based)

Getting Date Components

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const now = new Date();
console.log(now.getFullYear());  // 2025
console.log(now.getMonth());     // 3 (April)
console.log(now.getDate());      // 30
console.log(now.getDay());       // 3 (Wednesday)
console.log(now.getHours());     // e.g., 14

Setting Date Components

Method	Description
`getFullYear()`	Year (e.g., 2025)
`getMonth()`	Month (0 = Jan, 11 = Dec)
`getDate()`	Day of the month (1-31)
`getDay()`	Day of the week (0 = Sun)
`getHours()`	Hour (0–23)
`getMinutes()`	Minutes (0–59)/td> </tr>
`getSeconds()`	Seconds (0–59)
`getMilliseconds()`	Milliseconds (0–999)
`getTime()`	Milliseconds (0–999)

Method	Description
`getFullYear()`	Year (e.g., 2025)
`setMonth()`	Set the month (0–11)
`setDate()`	Set the day of the month
`setHours()`	Set the hours
`setMinutes()`	Set the minutes
`setSeconds()`	Set the seconds

const d = new Date();
d.setFullYear(2030);
d.setMonth(0); // January
d.setDate(1);

Formatting Dates

JavaScript doesn't have built-in formatting like "dd/mm/yyyy", but you can manually format:

const d = new Date();
const day = d.getDate();
const month = d.getMonth() + 1;
const year = d.getFullYear();
                                    
const formatted = `${day}/${month}/${year}`;
console.log(formatted); // e.g., 30/4/2025

Date Comparison

const d1 = new Date("2024-01-01");
const d2 = new Date("2025-01-01");
                                    
console.log(d1 < d2); // true

Calculating Time Differences

You can subtract two dates to get the time in milliseconds.

const start = new Date("2025-01-01");
const end = new Date("2025-02-01");
                                    
const diffInMs = end - start;
const diffInDays = diffInMs / (1000 * 60 * 60 * 24);
                                    
console.log(diffInDays); // 31

Auto-Correction

JavaScript adjusts invalid dates automatically:

const d = new Date(2025, 0, 32); // Jan 32 → auto-corrects to Feb 1
console.log(d); // Sat Feb 01 2025

Converting to String

Method	Example Output
`toString()`	`"Wed Apr 30 2025 10:30:00 GMT+..."`
`toDateString()`	`"Wed Apr 30 2025"`
`toTimeString()`	`"10:30:00 GMT+..."`
`toISOString()`	`"2025-04-30T10:30:00.000Z"`

🧪 Practice Exercise:

Task:

Create a new date for your birthday.
Print the current year, month, and date using get...() methods.
Calculate how many days are left until New Year.
Compare two dates to check which comes first.
Format today’s date as "DD-MM-YYYY" using string interpolation.

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