Understanding Date and Time in JavaScript

JavaScript, however, understands the date based on a timestamp derived from Unix time , which is a value consisting of the number of milliseconds that have passed since midnight on January 1st, 1970. We can get the timestamp with the getTime() method.

// Get the current timestamp
now.getTime();
Output
1508330494000
The large number that appears in our output for the current timestamp represents the same value as above, October 18th, 2017.
Epoch time, also referred to as zero time, is represented by the date string 01 January, 1970 00:00:00 Universal Time (UTC), and by the 0 timestamp. We can test this in the browser by creating a new variable and assigning to it a new Date instance based on a timestamp of 0.
epoch.js




    

// Assign the timestamp 0 to a new variable
const epochTime = new Date(0);
epochTime;
Output
01 January, 1970 00:00:00 Universal Time (UTC)
Epoch time was chosen as a standard for computers to measure time by in earlier days of programming, and it is the method that JavaScript uses. It is important to understand the concept of both the timestamp and the date string, as both may be used depending on the settings and purpose of an application.
So far, we learned how to create a new Date instance based on the current time, and how to create one based on a timestamp. In total, there are four formats by which you can create a new Date in JavaScript. In addition to the current time default and timestamp, you can also use a date string, or specify particular dates and times.
Date Creation
Output