javascript日期操纵怪异

Question

I want to create two dates that contain the beginning date of a month and the beginning date of the following month. This is what I have:

var TheMonth = "6.2012"; // as in june 2012
TheMonth = TheMonth.split(".")

var TheDisplayDate = new Date(parseInt(TheMonth[1], 10), (parseInt(TheMonth[0], 10) - 1), 1);

var TheUpperLimit = new Date(TheDisplayDate.getFullYear(), TheDisplayDate.getMonth(), 1);

//I'm adding a month here but it's not changing the month
TheUpperLimit.setMonth(TheUpperLimit.getUTCMonth() + 1);

The problem is that TheUpperLimit turns out to be the same date. I have a fiddle here to look at. What am I doing wrong?

Thanks.

Answer 1

The problem is that you use getUTCMonth with setMonth instead of setUTCMonth . It's more correct to use only UTC or only non-UTC methods together. When you use setMonth and getMonth , it seems to work correct. But when you use UTC variations of these functions, it gives you 2 jul instead of 1 jul (in my time zone, at least). I suggest you to use the following code to avoid complications with time:

var TheMonth = "6.2012"; // as in june 2012
TheMonth = TheMonth.split(".");
var month = parseInt(TheMonth[0]);
var year = parseInt(TheMonth[1]);
var second_month = month + 1;
var second_year = year;
if (second_month > 12) {
    second_month = 1;
    second_year++;
}

var TheDisplayDate = new Date(year, month - 1, 1);
var TheUpperLimit = new Date(second_year, second_month - 1, 1);
console.log([TheDisplayDate, TheUpperLimit]);
// => [Date {Fri Jun 01 2012 00:00:00 GMT+0400 (MSK)}, 
//     Date {Sun Jul 01 2012 00:00:00 GMT+0400 (MSK)}]

Answer 2

According to your nick( @frenchie ), your local time is probably French time. This means GMT + 2:00 .

When you are setting for example:

new Date(2012,5,1)

it means you have:

year=2012, month=June, day=1, hours=minutes=seconds=mseconds=0 

As GMT + 2:00 , UTC Date will have -2 hours offset. If you would do TheUpperLimit.toString() , you will see, that you have Thu, 31 May 2012 22:00:00 GMT . This means, your UTC Month is '4'. So when you are adding '+1' you will have '5' for month and it was June.So there is nothing wierd.