javascript - Why isn't my date parsing correctly? - Stack Overflow

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I'm having issues parsing dates after 01/01/2000. The results are being returned incorrectly. 1999 is getting parsed as the year 1999, when it gets to 2000 it is parsing it as 0100, and then 2001 as 0101, etc. Here is the test code to illustrate this issue:

<script type="text/javascript" language="javascript">


// functions incorrect  changes year from 2010 to 0101
var d = (new Date("12/01/2009"));
if (d.getMonth() < 11) 
 { d = new Date(d.getYear(), d.getMonth() + 1, 1); } 
 else
 { d = new Date(d.getYear() + 1, 0, 1); } 
document.write(d);
//  Result:  Sat Jan 01 0101 00:00:00 GMT-0500 (Eastern Standard Time) 

document.write('<br />');


document.write(Date.parse(Date()) < Date.parse(d));
// 
// Result: false  today should definitely be < 01/01/2010


document.write('<br />');


// Functions correctly if year is before 2000

var d = (new Date("12/01/1998"));

if (d.getMonth() < 11) 
 { d = new Date(d.getYear(), d.getMonth() + 1, 1); } 
 else
 { d = new Date(d.getYear() + 1, 0, 1); } 


document.write(d);
//  Result:  Fri Jan 01 1999 00:00:00 GMT-0500 (Eastern Standard Time)  
document.write('<br />');


document.write(Date.parse(Date()) < Date.parse(d));
// false


</script>

I'm having issues parsing dates after 01/01/2000. The results are being returned incorrectly. 1999 is getting parsed as the year 1999, when it gets to 2000 it is parsing it as 0100, and then 2001 as 0101, etc. Here is the test code to illustrate this issue:

<script type="text/javascript" language="javascript">


// functions incorrect  changes year from 2010 to 0101
var d = (new Date("12/01/2009"));
if (d.getMonth() < 11) 
 { d = new Date(d.getYear(), d.getMonth() + 1, 1); } 
 else
 { d = new Date(d.getYear() + 1, 0, 1); } 
document.write(d);
//  Result:  Sat Jan 01 0101 00:00:00 GMT-0500 (Eastern Standard Time) 

document.write('<br />');


document.write(Date.parse(Date()) < Date.parse(d));
// 
// Result: false  today should definitely be < 01/01/2010


document.write('<br />');


// Functions correctly if year is before 2000

var d = (new Date("12/01/1998"));

if (d.getMonth() < 11) 
 { d = new Date(d.getYear(), d.getMonth() + 1, 1); } 
 else
 { d = new Date(d.getYear() + 1, 0, 1); } 


document.write(d);
//  Result:  Fri Jan 01 1999 00:00:00 GMT-0500 (Eastern Standard Time)  
document.write('<br />');


document.write(Date.parse(Date()) < Date.parse(d));
// false


</script>

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Share Improve this question Follow edited Aug 23, 2011 at 20:00 Stephen 1,61722 gold badges1818 silver badges4444 bronze badges asked Mar 13, 2009 at 19:26 stephenbayerstephenbayer 12.4k1515 gold badges6666 silver badges9999 bronze badges

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3 Answers 3

Sorted by: Reset to default 5

You need to use d.getFullYear() instead of d.getYear()

getYear() only gives the number of years since 1900, obviously ;)

You should be using Date.parse(). Part of why you're seeing odd results is because you use new Date("12/01/2009") up at the top and pare everything else to that. Note that Date.parse() returns a number, not a date object. Therefore, do this for your very first assignment:

var d = new Date(Date.parse("12/01/2009"));

The next part is that you need the getFullYear() function rather than just getYear(), though your problem there is only in your verification code, not in how you actually parse the date.

what getYear() returns is browser-dependent. Try d.getFullYear() instead.

A reasonable Javascript date reference: http://www.w3schools./jsref/jsref_obj_date.asp

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