Count down script time inaccuracy

[covana]

I have a simple countdown script that takes an parameter for the expiration date and creates a count down from now until the expiration. Everything is handled using unix timestamps.

here is the javascript

function countdown(exp_time){
	var now = Math.round(new Date().getTime() / 1000);
	//alert(now);
	var time_til = exp_time - now;
	if(time_til > 0){
	
		days = Math.floor(time_til/(60*60*24));
		
		time_til %= (60*60*24);
		
		hours = Math.floor(time_til/(60*60));
		
		time_til %= (60*60);
		
		minutes = Math.floor(time_til/60);
		
		time_til %= 60;
		
		seconds = time_til;
		
	document.getElementById('count_update').innerHTML = days +':'+hours+':'+minutes+':'+seconds;
	
		setTimeout('countdown('+exp_time+');', 1000);
	}
	else{
		document.getElementById('count_update').innerHTML = 'No Time Remaining!';
	}
}

the parameter is passed in using php like this

$expired = mktime(0,0,0,MM,DD,YYY);


<div id='count_update'></div>
<script type='text/javascript'>countdown(<?php echo $expired]; ?>)</script>

Where MM, DD, YYYY in the mktime function are whatever is pulled from the database.

The script seems to work fine except for one thing. The time shown on the countdown does not expire at 12am on the servers clock. Its anywhere from 1 to 4 hours off depending on the server it is running on. Am I over looking something that I should be adding in the js to make the clock accurrate?

Thanks alot for any help

-Kyle

[BIOSTALL]

After playing with this for a while it appears GMT has something to do with the offset, hence it's always exactly 1 hour out.

Try changing:

var now = Math.round(new Date().getTime() / 1000);

To:

var now = new Date();
var offset = now.getTimezoneOffset();
	
var now = Math.round(new Date().getTime()/1000)-(offset*60);

That will get the difference in the timezone and factor that into the final calculation.

Hope that helps somewhat

[BIOSTALL]

Please note, your code will also currently generate a PHP parse error due to the following bit of code:

PHP Code:

<?php echo $expired]; ?>

Just remove the closing square bracket.

[covana]

Originally Posted by BIOSTALL

Please note, your code will also currently generate a PHP parse error due to the following bit of code:

PHP Code:

<?php echo $expired]; ?>

Just remove the closing square bracket.

Thanks a lot. I believe you additions have made it more accurate. The parse error was just in the sample code there. I am actually pulling the expiration date from a stored value in the database. I just forgot to remove the ] when editing the code to post here as an example.

Thanks again

[covana]

Still not sure if it is exactly right. Should I be accounting for time zone offsets when i store the expiration date in the database and not just use mktime() alone?

[BIOSTALL]

You should store the date/time generated by PHP (ie. the server time) rather than what is generated by Javascript (ie. the time of the users computer).