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I am using JS to calculate my date diffrence but i did not get the rounded value please guide me. Formula used to find the Approximate amount

value1 = todate - fromdate;
value2 = value1 / 30;
value3 = value2 * 5000;

for this i am using the following code

 var preioddiff = parseInt(todate ) - parseInt(fromdate);
 var dividen = preioddiff / 30;
 var totappamt =  dividen * parseInt(5000);

but it does not give the correct answer

for example From Date is 04012011 and to date is 04022011 if i subtract the value using the parseInt(todate ) - parseInt(fromdate); it return the value 13303380 instead of 0001000

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  • Are todate and fromdate strings, or are they Date objects? What is displayed if you do alert(parseInt(todate))? Also, aren't you expecting preioddiff to be 10000, not 1000? Commented Mar 19, 2011 at 6:45
  • If you subtract one Date object from another, you probably get the difference between them in milliseconds. Commented Mar 19, 2011 at 6:50
  • Never use parseInt without a second argument (usually 10). If you do, any string that starts with "0" will be interpreted as octal. This creates obscure bugs that are very hard to find. Although in this case your parseInt calls are totally unnecessary as your arguments are already numbers. Commented Mar 19, 2011 at 7:42

4 Answers 4

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Please explain your logic, Meena.

From what I see, your starting point is wrong.

You can't treat a date formatted as a string in the form "MMDDYYYY" and expect to be able to subtract them to do date calculations unless the two dates are in the same month. In that case, just deal with the days and ignore the year and month.

Your case: 04022011 - 04012011 == 0001000 (shouldn't that be 00010000 - note the extra zero at the end?)

What about: 04012011 - 03312011 - treating them as numbers, you'd get 00700000, but it should be that same as above since the two dates are only one day apart.

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3 Comments

Good comment! Shouldn't be an answer though. For this to be an answer, you should explain to OP how to parse those strings into dates which you can then compare. Just pointing out that date strings can't be compared should be done through a comment.
I don't even know what Meena's starting point is so how can I say Meena should do it this way or that? All Meena has shown is Act 2 of a 3-act play with a summary of Acts 1 and 3.
It is pretty clear, she has dates as strings in MMDDYYY and wants to know the difference between dates, she's just not thinking about it the right way
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You might have to specify the base number, like this:

var res =  parseInt('04022011', 10) - parseInt('04012011', 10);
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It isn't very clear exactly what you're trying to do, but here's how you can get the number of days between two JavaScript Date objects:

var d1 = new Date('March 1');
var d2 = new Date('March 19');
var days_diff = Math.round((d2 - d1)/86400000);
alert(days_diff); // output is 18

When you subtract one Date from another, you get the number of milliseconds between them. Note that not all days have the same number of milliseconds (because of daylight savings) and obviously, months have different numbers of days, so doing date calculations this way has its risks.

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If you are using parseInt to parse a date string that may start with "0", ALWAYS put in a second argument to specify a radix (usually 10).

The string you passed to parseInt will be interpreted as octal if it starts with a zero, which is what you have. You're never going to get correct results this way.

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