JavaScript | Date.parse()

The Date.parse() function is an inbuilt function in JavaScript which helps us to know the exact number of milliseconds that have passed since midnight, January 1, 1970, till the date we provide.
Syntax:

Date.parse(datestring);

Parameters: This function takes a parameter of datestring which is taken as the input.
Return Values: It returns an integer value representing the number of millisecond between midnight January 1, 1970, and the date provided. If by any means, the machine can’t recognize the string or the input string is invalid, it will return “NaN” instead of an integer.

JavaScript code to show the working of Date.parse() function:

Code #1:

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<script>
  
    // Taking a date string as input.
    var date = "February 18, 2018 12:30 PM";
      
    // Calling parse function on input date string.
    var msec = Date.parse(date);
    document.write(msec);
      
</script>

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Output:


1518937200000


Code #2:

If the input string of date is not correct, it return NaN i.e, not a number.











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<script> 


  


    // Taking wrong date string as input. 


    var date = "February 48, 2018 12:30 PM"; 


      


    // calling parse function. 


    var msec = Date.parse(date); 


    document.write(msec); 


      


</script>                     



















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Output:


NaN


Why 01 Jan 1970 00:00:00 GMT?

It is called the Unix time i.e. the time Unix was invented. Almost all the programming languages, operating systems use this as their reference starting time.

Note: Once we get the millisecond count between two dates, we can easily find the number of hours, days, months, years, etc by simple maths calculation.



          
          
          
          

            

    

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