Finding a serial number of a day.

**gits** · Aug 23 '10, 09:50 AM

may i ask what a 'serial number of a date of a year' is? never heard of it - could you give an example or link to it?

**Udara chathuranga** · Aug 23 '10, 11:13 AM

The serial number of 1900.01.01 is 1.
The serial number of 1901.01.01 is 365.
Serial number is the system assigned number for a date from the day 1900.01.01

**gits** · Aug 23 '10, 01:42 PM

in that case it is basically the day difference to the base date. a simple way could be to extend the JavaScript date object like this:

Code:

Date.prototype.getSerialDateNumber = function() {
    var baseDate = new Date(1900,1,1);
    
    // one day based on ms
    var oneDay = 86400000;

    var dayDiff = Math.ceil(
        (this.getTime() - baseDate.getTime()) / oneDay
    );

    return dayDiff;
}

var d = new Date;

alert(d.getSerialDateNumber());

**Udara chathuranga** · Aug 25 '10, 07:46 PM

Code:

<html><head><title>Day counter</title>
<script language="javascript">
   Date.prototype.getSerialDateNumber = function() {
       var baseDate = new Date(1900,1,1);
	   //this is the date that i want to find the serial number--------I add this
	var mydate=new Date(1900,1,31);
    // one day based on ms
    var oneDay = 86400000;


       var dayDiff = Math.ceil(
         (mydate.getTime() - (baseDate.getTime()-oneDay)) / oneDay 
		 //"oneDay" should be abstracted from baseDate.getTime() to get the right answer isn't it...
    );

 
     return dayDiff;

 }
  
  var d = new Date;
  
 alert(d.getSerialDateNumber());
 
</script>
</head>
<body>
</body>
</html>

Thank you very much sir, I understood your code and I have done some changes On it. Is it a good change or a bad one. Please reply. How ever thank you very much for your help.

**gits** · Aug 25 '10, 08:27 PM

it works for this case ... but you wouldn't have needed it ... in line 21 of your last code post the following would have done the job:

Code:

var d = new Date(1900,1,31);

your change fixes the output to a specific date and makes the date-extension nearly useless ... which could give you the serial date number for any date without your change - so ... you might judge your change for yourself ... what would you say? bad or good change? :)

**gits** · Aug 25 '10, 09:41 PM

ahh ... and we need a fix for the baseDate:

Code:

new Date(1900,1,1)

// is: Thu Feb 01 1900 00:00:00 GMT+0100 (CET)

// while:

new Date(1900,0,1)

// is: Mon Jan 01 1900 00:00:00 GMT+0100 (CET)

so the month starts at 0 for january ... just overlooked it before :) you might have a look here for a reference to the JavaScript Date object.

**Udara chathuranga** · Aug 26 '10, 06:37 PM

Thanks, Now your code is working properly. Please be in touch.

Finding a serial number of a day.

Finding a serial number of a day.

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