how to: timezones?

[jasondavis]

Im wondering how to go about adding a timezone setting for users to my site, currently an example time showed on my site is this

2007-08-07 07:44:54

I would like someone on Eastern standerd time -5 be able to pick this as an option and adjust time time sitewide, any insight on how to do this the most efficient way for a very hight traffic site

[devinemke]

store the timezone in a session variable as a simple integer (+ or - depending on which side of greenwhich they are) then just add/substract from your timestamps.

[jasondavis]

Thats what I was thinking but thanks for clarifying

So 1 example on my site I have

<?=$line_announcement['submitdate']?>

which shows

2007-08-02 09:21:27

hiw would I -5 for example from that?

[devinemke]

i suggest that you store all of the dates/times as GMT then do something like:

$gmt = '2007-08-02 09:21:27';
echo date('Y-m-d H:i:s', strtotime($gmt) - (5 * (60 * 60)));

[jasondavis]

$gmt = '2007-08-02 09:21:27';
echo date('Y-m-d H:i:s', strtotime($gmt) - ($timezonesetting * (60 * 60))); 

so would this be correct to have there timezone setting in place? and - value would work to like -6 (60 60) ?

[devinemke]

a simple example:

function tz_adjust($gmt, $offset)
{
	$date = date('Y-m-d H:i:s', strtotime($gmt) + ($offset * 3600));
	return $date;
}

$gmt = '2007-08-02 12:00:00';

echo tz_adjust($gmt, -5) . '<br>';
echo tz_adjust($gmt, 7) . '<br>';

[jasondavis]

thank you