JavaScript has a built-in `Date` object that you can use to create and manipulate dates and times.
You can create a new `Date` object as follows:
```
// create a new date object with current date and time
let now = new Date();
console.log(now); // output: current date and time
```
You can also create a new `Date` object from a specific date and time:
```
// create a new date object with specific date
let specificDate = new Date(‘2015-03-25T12:00:00’);
console.log(specificDate); // output: Wed Mar 25 2015 12:00:00 GMT+0000 (Coordinated Universal Time)
```
The `Date` object provides several methods for getting and setting individual parts of a date and time, such as the year, month, day, hours, minutes, seconds, and milliseconds.
Here are some examples:
```
let now = new Date();
// get parts of the date
console.log(now.getFullYear()); // output: current year
console.log(now.getMonth()); // output: current month (0-based, 0 = January)
console.log(now.getDate()); // output: current day of the month
console.log(now.getHours()); // output: current hour
console.log(now.getMinutes()); // output: current minutes
console.log(now.getSeconds()); // output: current seconds
console.log(now.getMilliseconds()); // output: current milliseconds
// set parts of the date
now.setFullYear(2020); // set the year to 2020
now.setMonth(0); // set the month to January
now.setDate(1); // set the day of the month to 1
now.setHours(0); // set the hour to 0
now.setMinutes(0); // set the minutes to 0
now.setSeconds(0); // set the seconds to 0
now.setMilliseconds(0); // set the milliseconds to 0
```
It’s important to note that JavaScript date and time is based on a time value that is milliseconds since 01 January, 1970 UTC.
Also, JavaScript dates are calculated in milliseconds. For example, 1 day is 86,400,000 milliseconds.
