CODEWITHSUNDEEP
javascript
fumeng
fumeng

Reputation: 1820

Comparing two dates in different timezones

I'm comparing two dates; one returned as a UTC String (as part of an Ajax response) and the second in local browser time:

Basically, I want to see if the date returned (endTime) happened before right now. My code is below and I thought I had it right but it's not working. 

var isActive = true;
var buffer   = 30000; // 30 seconds
var endTime = new Date(Date.parse(response.endTime)); // Fri Oct 23 2015 12:01:14 GMT-0400 (EDT)
var now = new Date(); // Thu Oct 22 2015 20:01:31 GMT-0400 (EDT)
var nowUtc = new Date(now).toUTCString(); // "Fri, 23 Oct 2015 00:01:31 GMT"
var nowTimeMs = new Date(nowUtc).getTime(); // 1445558491000
var endTimeMs = endTime.getTime() + buffer; // 1445616104000

if(  nowTimeMs > endTimeMs  ){
    isActive = false;
}

isActive should remain as true but instead it's false. I feel like I've been looking at this too long and am missing something very simple. Am I?

Thanks for any helpful tips.

Update: Based on the responses I thought I'd update my question. What is the best way to compare two dates where one is this: 

new Date(); // Thu Oct 22 2015 21:51:53 GMT-0400 (EDT)

...and the other is a String representation of date:

"2015-10-23 01:49:27"

I figure the best way to create a valid Date object out of the String is using this code. 

isThisActive:function(p){
    var isActive = true;
    var buffer   = 30000;
    var pEndTime = myObj.parseStringAsDate(p.callEndTime);
    var now      = new Date();
    var offset   = now.getTimezoneOffset() * 60000;
    now.setTime( now.getTime() + offset );

    var nowTimeMs = now.getTime();
    var endTimeMs = pEndTime.getTime() + buffer;

    if(  nowTimeMs > endTimeMs  ){
        isActive = false;
    }
    return isActive;
},
parseStringAsDate:function(str){
    var dateTimeStr = str.split(" ");
    var dateStr     = dateTimeStr[0].split("-");
    var year        = dateStr[0];
    var month       = dateStr[1];
    var day         = dateStr[2];
    var timeStr     = dateTimeStr[1].split(":");
    var hours       = timeStr[0];
    var minutes     = timeStr[1];
    var seconds     = timeStr[2];

    return new Date( year,month,day,hours,minutes,seconds);
}

Because "pEndTime" is in UTC I applied the offset to the "now" Date object but even this is not working. Where's the problem here? I thought this would solve it.

SOLVED: The latest code I posted did work. I was just getting incorrect values for the response.endTime (It wasn't converted to correct military time). Thank you everyone for your input. I've tried to upgrade as many helpful responses as I could.

Upvotes: 1

Views: 115

Answers (4)

Nhat Hong Ly
Nhat Hong Ly

Reputation: 628

I usually use moment.js in my projects which related to formatting date time, especially in the reports (I'm working in the field of finance). You must have one more library in your project but it provides many other functionalities

Sorry, this is for your new update. I haven't got enough 'population' to leave a comment :P

Upvotes: 1

RobG
RobG

Reputation: 147373

You should not use the Date constructor or Date.parse (which do the same thing) to parse date strings. Either write your own parse function (below) or use a well maintained library.

To parse the format in the OP, you can use:

// Parse  Thu Oct 22 2015 20:01:31 GMT-0400 (EDT)
function parseMMMDY(s) {
    var b = s.split(/\W/);
    var months = {jan:0,feb:1,mar:2,apr:3,may:4,jun:5,jul:6,aug:7,sep:8,oct:9,nov:10,dec:11};
    var sign = /GMT-\d{4}/i.test(s)? 1 : -1;
    var min = +b[5] + (sign * b[8].slice(0,2) * 60 ) + (sign * b[8].slice(-2)); 
    return new Date(Date.UTC(b[3], months[b[1].toLowerCase().slice(0,3)], b[2], b[4], min, b[6]));
}

document.write(parseMMMDY('Thu Oct 22 2015 20:01:31 GMT-0400 (EDT)'));

Upvotes: 1

Nhat Hong Ly
Nhat Hong Ly

Reputation: 628

I think the problem is here:

var endTime = new Date(Date.parse(response.endTime));

respnonse.endTime is UTC, right? But when you parse it to Date value, Date.parse assumes it is in local timezone (GMT-0400 as in your example code). It means that the endDate gets the wrong value

Upvotes: 1

jkris
jkris

Reputation: 6521

var endTime = new Date(Date.parse(response.endTime)); // Fri Oct 23 2015 12:01:14 GMT-0400 (EDT) var now = new Date(); // Thu Oct 22 2015 20:01:31 GMT-0400 (EDT)

Your endTime doesn't seem to return a UTC date as you mentioned. It looks to be using (EDT) so maybe you didn't have to convert it to UTC.

Upvotes: 0

Related Questions