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Javascript and mySQL dateTime stamp difference

I have a mySQL database in which I store the time in this format automatically:
2015-08-17 21:31:06
I am able to retrieve this time stamp from my database and bring it into javascript. I want to then get the current date time in javascript and determine how many days are between the current date time and the date time I pulled from the database.
I found this function when researching how to get the current date time in javascript:
Date();
But it seems to return the date in this format:
Tue Aug 18 2015 10:49:06 GMT-0700 (Pacific Daylight Time)
There has to be an easier way of doing this other than going character by character and picking it out from both?

You can build a new date in javascript by passing the data you receive from your backend as the first argument.
You have to make sure that the format is an accepted one. In your case we need to replace the space with a T. You may also be able to change the format from the back end.
Some good examples are available in the MDN docs.
var d = new Date("2015-08-17T21:31:06");
console.log(d.getMonth());
To calculate the difference in days you could do something like this:
var now = new Date();
var then = new Date("2015-08-15T21:31:06");
console.log((now - then)/1000/60/60/24);

You can select the difference directly in your query:
SELECT DATEDIFF(now(), myDateCol) FROM myTable;

the Date object has a function called getTime(), which will give you the current timestamp in milliseconds. You can then get the diff and convert to days by dividing by (1000 * 3600 * 24)
e.g.
var date1 = new Date()
var date2 = new Date()
var diffInMs = date2.getTime() - date1.getTime()
var diffInDays = diffInMs/(1000*3600*24)

Since none of the other answer got it quite right:
var pieces = "2015-08-17 21:31:06".split(' ');
var date = pieces[0].split('-');
var time = pieces[1].split(':');
var yr = date[0], mon = date[1], day = date[2];
var hour = time[0], min = time[1], sec = time[2];
var dateObj = new Date(yr, mon, day, hr, min, sec);
//if you want the fractional part, omit the call to Math.floor()
var diff = Math.floor((Date.now() - dateObj.getTime()) / (1000 * 60 * 60 * 24));
Note that none of this deals with the timezone difference between the browser and whatever you have stored in the DB. Here's an offset example:
var tzOff = new Date().getTimezoneOffset() * 60 * 1000; //in ms

Comparing two dates in JavaScript

I am currently trying to compare the launch_date with today's date. Let's say if the launch_date is within 3 years from today's date, it should perform something but I only managed to come out with some portion of the code:
var today = new Date();
var launch_date = 2011/10/17 00:00:00 UTC;
//if today's date minus launch_date is within 3 years, then do something.
Any guides? Thanks in advance.

To explicitly check for the three year range
var ld = new Date('2011/10/17 00:00:00 UTC')
if(today.getFullYear() - ld.getFullYear() < 3) {
//do something
}
This will fail on an invalid date string and possibly some other edge cases.
If you'll be doing a lot of date calculations I highly recommend Moment: http://momentjs.com/

you could always calculate the timespan in days and use that.
var getDays = function(startDate, endDate){
var ONE_DAY = 1000 * 60 * 60 * 24;
var difference = endDate.getTime() - startDate.getTime();
return Math.round(difference / ONE_DAY);
}
See this JsFiddle: http://jsfiddle.net/bj4Dq/1/

Try-
var today = new Date();
var launch_date = new Date("2011/10/17 00:00:00 UTC");
var diff = today.getYear() - launch_date.getYear();
if(diff <=3 )
alert("yes");
else
alert("no");
jsFiddle

you can create a Date object and invoke getTime() method (returns numer of milliseconds since 1970-01-01). Use one of this rows:
var yourDate = new Date(dateString) // format yyyy-mm-dd hh:mm:ss
var yourDate = new Date(year, month, day, hours, minutes, seconds, milliseconds)
After in the if statement use this condition:
var edgeDate = // new Date(dateString);
if ( (today.getTime () - yourDate.getTime ()) >= edgeDate.getTime() ){
// do something
}
Regards,
Kevin

Time between two times on current date

I am trying to calculate the time between two times on the current date using JavaScript. There are other questions similar to this one, but none seem to work, and few with many upvotes that I can find.
I have the following, which fails on the line: var diff = new Date(time1 - time2);, which always gives me an invalid Date when alerted, so it is clearly failing. I cannot work out why.
The initial date is added in the format of: hh:mm:ss in an input field. I am using jQuery.
$(function(){
$('#goTime').click(function(){
var currentDate = new Date();
var dateString = (strpad(currentDate.getDate()) +'-'+ strpad(currentDate.getMonth()+1)+'-'+currentDate.getFullYear()+' '+ $('#starttime').val());
var time1 = new Date(dateString).getTime();
var time2 = new Date().getTime();
var diff = new Date(time1 - time2);
var hours = diff.getHours();
var minutes = diff.getMinutes();
var seconds = diff.getMinutes();
alert(hours + ':' + minutes + ':' + seconds);
});
});
function strpad(val){
return (!isNaN(val) && val.toString().length==1)?"0"+val:val;
}
dateString is equal to: 14-01-2013 23:00

You have the fields in dateString backwards. Swap the year and day fields...
> new Date('14-01-2013 23:00')
Invalid Date
> new Date('2013-01-14 23:00')
Mon Jan 14 2013 23:00:00 GMT-0800 (PST)

dd-MM-yyyy HH:mm is not recognized as a valid time format by new Date(). You have a few options though:
Use slashes instead of dashes: dd/MM/yyyy HH:mm date strings are correctly parsed.
Use ISO date strings: yyyy-MM-dd HH:mm are also recognized.
Build the Date object yourself.
For the second option, since you only really care about the time, you could just split the time string yourself and pass them to Date.setHours(h, m, s):
var timeParts = $('#starttime').val().split(':', 2);
var time1 = new Date();
time1.setHours(timeParts[0], timeParts[1]);

You are experiencing an invalid time in your datestring. time1 is NaN, and so diff will be. It might be better to use this:
var date = new Date();
var match = /^(\d+):(\d+):(\d+)$/.exec($('#starttime').val()); // enforcing format
if (!match)
return alert("Invalid input!"); // abort
date.setHours(parseInt(match[1], 10));
date.setMinutes(parseInt(match[2], 10));
date.setSeconds(parseInt(match[3], 10));
var diff = Date.now() - date;

If you are trying to calculate the time difference between two dates, then you do not need to create a new date object to do that.
var time1 = new Date(dateString).getTime();
var time2 = new Date().getTime();
var diff = time1 - time2;// number of milliseconds
var seconds = diff/1000;
var minutes = seconds/60;
var hours = minutes/60;
Edit: You will want to take into account broofa's answer as well to
make sure your date string is correctly formatted
The getTime function returns the number of milliseconds since Jan 1, 1970. So by subtracting the two values you are left with the number of milliseconds between each date object. If you were to pass that value into the Date constructor, the resulting date object would not be what you are expecting. see getTime

Get date time for a specific time zone using JavaScript

It seems that JavaScript's Date() function can only return local date and time. Is there anyway to get time for a specific time zone, e.g., GMT-9?
Combining #​Esailija and #D3mon-1stVFW, I figured it out: you need to have two time zone offset, one for local time and one for destination time, here is the working code:
var today = new Date();
var localoffset = -(today.getTimezoneOffset()/60);
var destoffset = -4;
var offset = destoffset-localoffset;
var d = new Date( new Date().getTime() + offset * 3600 * 1000)
An example is here: http://jsfiddle.net/BBzyN/3/

var offset = -8;
new Date( new Date().getTime() + offset * 3600 * 1000).toUTCString().replace( / GMT$/, "" )
"Wed, 20 Jun 2012 08:55:20"
<script>
var offset = -8;
document.write(
new Date(
new Date().getTime() + offset * 3600 * 1000
).toUTCString().replace( / GMT$/, "" )
);
</script>

You can do this in one line:
let d = new Date(new Date().toLocaleString("en-US", {timeZone: "timezone id"})); // timezone ex: Asia/Jerusalem

var today = new Date();
var offset = -(today.getTimezoneOffset()/60);

You can always get GMT time (so long as the client's clock is correct).
To display a date in an arbitrary time-zone, construct a string from the UTC hours, minutes, and seconds after adding the offset.

There is simple library for working on timezones easily called TimezoneJS can be found at https://github.com/mde/timezone-js.

Get time difference in javascript ISO format

I have a datetime in ISO format i.e.
2012-06-26T01:00:44Z
I want to get the time difference from current time. How can I achieve this using javascript or javascript library Date.js or jquery

This will give you the difference in milliseconds, you can then format it as you want
var diff = new Date("2012-06-26T01:00:44Z") - new Date();

Try this:
var someDate = new Date("2012-06-26T01:00:44Z");
var now = new Date();
var one_day = 1000 * 60 * 60 * 24;
var diff = Math.ceil((someDate.getTime()-now .getTime())/(one_day))
alert(diff)
Example fiddle
You can obviously amend the one_day variable to get the difference in the unit you require.

I would suggest converting ISO format to something that works cross browser.
Try this,
var d = "2012-06-26T01:00:44Z";
var someDate = new Date(d.replace(/-/g,'/').replace('T',' ').replace('Z',''));
alert(someDate - new Date());
Edit:
I guess, you need pretty time
Try this awesome code
Edit 2:
You needed reverse, so try this instead
var old_date = new Date();
alert('Old date: ' + old_date.toGMTString())
var new_date = new Date(old_date.setMinutes(old_date.getMinutes() - 5));
alert('Date 5 minutes before: ' + new_date.toGMTString());
If you need timestamp,
alert(new_date.getTime());

in order to format date you can use this function to get the desire format of the date and you can easily change the position of day , month and year.
function convertFormat(inputDate)
var date = new Date(inputDate);
var day = date.getDate();
var month = date.getMonth()+1;
var year = date.getFullYear();
var fullYear = year + '/' + month + '/' + day
return fullYear;