Question

im writing a small calendar based on php and jquery which has the a function to calculate the time difference and display a popup 15 minutes before.

Can some one tell me how can i calculate the time difference in minutes and popup 15 minutes before.

my time is saved as

18-07-2012 15:13:54

Answer 1

jsBin demo

var php = '19-07-2012 03:00:00'.split('-');
var phpDate   = php[1]+'/'+php[0]+'/'+php[2];
var phpTime   = new Date(phpDate).getTime();
var currTime  = new Date().getTime();
var difference= phpTime-currTime; 
var leftMin   = Math.ceil( difference/(1000*60) );

$('#test').text(leftMin+' MINUTES LEFT!');

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Code explanation:

To get the remaining time I’ve done a millisecond comparison of the php returned time in milliseconds from Jan. 1 1970
and the current time in ms from Jan 1 1970 – subtracting the two values and getting the milliseconds difference. To calculate that difference in minutes I’ve just done:

 var leftMin   = Math.ceil( difference/(1000*60) );

The trick was to get the right time format and to revert your (php) returned time to that format too.
The default format looks like: MONTH/DAY/YEAR HOURS:MINUTES:SECONDS

To convert the php returned time '19-07-2012 03:00:00'to that one, I used:

var php = '19-07-2012 03:00:00'.split('-');   // split in array fractions
var phpDate   = php[1]+'/'+php[0]+'/'+php[2]; // reposition array keys and add '/'

which returns: 07/19/2012 03:00:00 and now we can compare it to the current time e.g.:

           07/19/2012 03:45:21

To retrieve the ms from your converted php time we can use:

var phpTime   = new Date(phpDate).getTime();  // get "ms from our string

and for the current time we just take:

var currTime  = new Date().getTime();         // get "ms from 1/1/1970

Now having our two milliseconds values we can simply subtract them to get the remaining time:

var difference= phpTime-currTime;