How to do Year / Month Calculations in Javascript?

Question

We have a Year/Month HTML control. The underlying value is kept as a decimal. For Example: 15 year and 2 months is equal to "15.02".

We want to do calculations based on 2 year/month controls (add/substract).

Just doing basic math calculations doesn't work:

  Value1 : 65.00
  Value2 : 47.09
  65.00 - 14.09 = 17.91 

 (is wrong, but should be 17.03 or (64.12 - 47.09))

Are there any Javscript/Jquery functions for that or a library that I can use to do Year / Month calculations ?

score 2 · Answer 1 · answered Sep 24 '12 at 07:37

2

Have a look at DateJS: http://code.google.com/p/datejs/wiki/APIDocumentation

answered Sep 24 '12 at 07:37

Evan Trimboli

29,900
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Great JS library for date functions. – Chris Dixon Sep 24 '12 at 07:53

Anusha · Answer 2 · 2012-09-24T08:00:20.357

0

The way you are calculating with decimals will not work! coz, JS consider that as a number not as a date..

To calculate Years or Months (basically any time/date system), you require the proper syntax. Visit this for the syntax

Hope this will work for you

edited Sep 24 '12 at 08:00

answered Sep 24 '12 at 07:46

Anusha

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3
20

score 0 · Answer 3 · answered Sep 24 '12 at 07:51

Just convert the month portion to regular decimal (divide by 12), do the maths, then convert the decimal fraction back to months (multiply by 12).

You'll have to parse the bits out with something like var bits = Value1.split(".");. The year would be bits[0] and month bits[1].

E.g. 47.09 would be 47 + (9 / 12 = 0.75) = 47.75.

So 65 - 47.75 = 12.25.

Convert decimal fraction part back to months: 0.25 * 12 = 0.3. So answer is 47.03.

score 0 · Answer 4 · edited May 23 '17 at 12:12

JavaScript doesn’t support operator overloading, so I don’t think you’ll be able to find a solution that allows you to literally use + and - with composite year/month values.

However, you could define your own year/month object type with add and subtract methods:

function YearsMonths(years, months) {
    this.years = years;

    if (months > 11) {
        this.years = this.years += Math.floor(months/12);
        this.months = months % 12;
    }
    else {
        if (months < 0) {
            this.months = 12 + (months % -12);
            this.years -= (Math.floor(months/-12) + 1);
        }
        else {
            this.months = months;
        }
    }
}

YearsMonths.prototype.add = function (otherYearsMonths) {
    newYears = this.years + otherYearsMonths.years;
    newMonths = this.months + otherYearsMonths.months;

    return new YearsMonths(newYears, newMonths);
}

YearsMonths.prototype.subtract = function (otherYearsMonths) {
    var newYears = this.years - otherYearsMonths.years,
        newMonths = this.months - otherYearsMonths.months;

    return new YearsMonths(newYears, newMonths);
}

And then use it like this:

value1 = new YearsMonths(65, 0);
value2 = new YearsMonths(47, 9);

value3 = value1.subtract(value2);
value4 = value1.add(value2);

value3.years;
# 17
value3.months;
# 3

value4.years;
# 112
value4.months;
# 9

score 0 · Answer 5 · answered Sep 24 '12 at 08:21

Here you can try this. It basically checks if your numbers are just years or if they contain months. The script is just a template, you can continue it and improve it, create a function out of it, or define your own prototype. Just check the code, hope it helps.

http://jsfiddle.net/6pRGv/

score 0 · Accepted Answer · answered Sep 24 '12 at 08:27

0

var a = '65.00'.split('.');
var b = '47.09'.split('.');
a = a[0] * 12 + Number(a[1]);
b = b[0] * 12 + Number(b[1]);
c = a - b;
c = Math.floor(c / 12) + (c % 12) / 100;

answered Sep 24 '12 at 08:27

timidboy

1,702
1
16
27

How to do Year / Month Calculations in Javascript?

6 Answers6