JavaScript Date & Time Functions
JavaScript provides a powerful built-in Date object to work with dates, times, and timestamps. You can create, read, format, and compute differences between dates easily.
What is the Date Object?
The Date object represents a moment in time. It stores the number of milliseconds since 1 January 1970 (UTC) and provides methods to read or change individual parts like year, month, hours and minutes.
Ways to Create a Date
Current Date
new Date() – right now.
From String
new Date("2025-08-15") – ISO format.
From Numbers
new Date(2025, 7, 15, 10, 30)
From Timestamp
new Date(1700000000000)
Date.now()
Returns current timestamp in ms.
UTC
new Date(Date.UTC(2025,7,15))
Basic Features
- Months are 0-indexed: January = 0, December = 11.
- Days of week from
getDay(): Sunday = 0, Saturday = 6. getTime()returns milliseconds since 1 Jan 1970 UTC.toLocaleDateString()formats by locale automatically.
Common Date Methods
| Method | Returns | Example |
|---|---|---|
| getFullYear() | Year (4 digits) | 2025 |
| getMonth() | Month (0–11) | 7 (August) |
| getDate() | Day of month (1–31) | 15 |
| getDay() | Day of week (0–6) | 5 (Friday) |
| getHours() | Hour (0–23) | 10 |
| getMinutes() | Minute (0–59) | 30 |
| getSeconds() | Seconds (0–59) | 45 |
| getTime() | Timestamp ms | 1755250200000 |
| toLocaleDateString() | Locale date | 15/8/2025 |
| toLocaleTimeString() | Locale time | 10:30:45 AM |
Exploring Date & Time Functions
In JavaScript, Date and Time functions are used to create, manage, manipulate, and format dates and times in web applications. They help developers build clocks, calendars, countdowns, schedulers, timers, and many real-time systems.
Importance of Date & Time Functions
- Handle time-sensitive data.
- Create clocks and countdowns.
- Manage appointments and schedules.
- Support localization and timezones.
- Useful in dashboards and analytics.
Important Date Functions
| Function | Description |
|---|---|
| new Date() | Creates current date object. |
| getDate() | Returns day of month. |
| getDay() | Returns weekday number. |
| getMonth() | Returns month value. |
| getFullYear() | Returns full year. |
| getHours() | Returns current hour. |
| getMinutes() | Returns current minutes. |
| getSeconds() | Returns current seconds. |
| Date.now() | Returns timestamp. |
Your First Date Program
<script> let d = new Date(); document.write( "Today is: " + d ); </script>
Example 1 : Format DD/MM/YYYY
<script> let d = new Date(); let day = d.getDate(); let mon = d.getMonth() + 1; let yr = d.getFullYear(); document.write( day + "/" + mon + "/" + yr ); </script>
Example 2 : Day Name
<script> let days = [ "Sun","Mon", "Tue","Wed", "Thu","Fri", "Sat" ]; let d = new Date(); document.write( "Today is " + days[d.getDay()] ); </script>
Example 3 : Current Time
<script> let d = new Date(); document.write( d.getHours() + ":" + d.getMinutes() + ":" + d.getSeconds() ); </script>
Example 4 : Today's Date
<button onclick="F()">
CLICK
</button>
<p id="d"></p>
<script>
function F(){
var d =
new Date();
var n =
d.getDate();
document
.getElementById("d")
.innerHTML = n;
}
</script>
Example 5 : getMinutes()
<button onclick="F()">
CHECK
</button>
<p id="d"></p>
<script>
function F(){
var d =
new Date();
var n =
d.getMinutes();
document
.getElementById("d")
.innerHTML = n;
}
</script>
Example 6 : UTC Hours
<button onclick="F()">
CHECK
</button>
<p id="d"></p>
<script>
function F(){
var d =
new Date();
var n =
d.getUTCHours();
document
.getElementById("d")
.innerHTML = n;
}
</script>
Example 7 : Live Clock
<p id="clk"></p>
<script>
setInterval(()=>{
let d =
new Date();
document
.getElementById("clk")
.innerText =
d.toLocaleTimeString();
},1000);
</script>
Important Notes
- getMonth() starts from 0.
- Use Date.now() for timestamps.
- padStart() helps formatting dates.
- Dates internally use UTC timezone.
Real-Life Use Cases
Clocks
Live dashboards and timers.
Calendars
Appointment and scheduling apps.
Countdowns
Exam and sale countdown timers.
Frequently Asked Questions
| Question | Answer |
|---|---|
| Why is getMonth() zero-based? | Months start from 0 in JavaScript. |
| Difference between Date.now() and new Date() ? | Date.now() returns timestamp only. |
| Is Date timezone aware? | Yes, dates use UTC internally. |
Conclusion
Date and Time functions are essential in JavaScript for building clocks, calendars, schedulers, countdowns, and dynamic web applications.
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