international time zones array

[wheeler]

i'm trying to use the DateTime listAbbreviations method (http://au.php.net/manual/en/datetime...reviations.php) to get an array of international timezones.

The problem is, the array is absolutely huge. Apparently there is alot of historical timezones stored, which i'm not really interested in. My question is, how can I go about getting a short list that represents all the time zones without having repetitive zones - is anyone aware of the important keys contained in the array? Surely i'm not forced to extract useful info out of this monster array?

[lampcms.com]

What do you mean by 'important keys'?

If there are many timezones with the same offset, how do you decide which one is more important that the other?

[wheeler]

well for example there is Currie and Linderman listed under Australia, both places i've never heard of that share the same time zone as Sydney which is the obvious choice for anyone in New South Wales. Additionally there is two listings for Sydney, 1 contains DST = true while the other is DST = false. DST should be true for Sydney, I have no idea why there is the two results.

[lampcms.com]

well for example there is Currie and Linderman listed under Australia, both places i've never heard of that share the same time zone as Sydney which is the obvious choice for anyone in New South Wales. Additionally there is two listings for Sydney, 1 contains DST = true while the other is DST = false. DST should be true for Sydney, I have no idea why there is the two results.

I see. I write a small class that extends timezone class in order to generate a nice looking drop-down list where user can select his own timezone.

I just added an option so you can define your own 'Important' zones.
You just have to fill the array 'addImportantZones' by hand and include only zones you want in it.
Then when you call $oTz = new clsTz();
$arrTz = $oTz->getSelectArray();

try it, see if it works for you.

class clsTZ extends DateTimeZone
{

	private $arrImportantZones = array(); // add names of important zones here
	
	public function getSelectArray(){
		$arrResult = array();
		$arr = self::listAbbreviations();

		foreach($arr as $abbr){
			foreach($abbr as $aTz){
				$key = $aTz['timezone_id'];
				if(!in_array($key, $this->arrImportantZones)){
					continue;
				}
				$sign   = ($aTz['offset'] < 0) ? '-' : ( ($aTz['offset'] > 0) ? '+' : '') ;
				$gmt   = abs($aTz['offset']) / 3600 ;
				$hh     = floor($gmt) ;
				$mm     = $gmt - $hh ;
				$mm  = floor($mm*60) ;

				$val = '(GMT'.$sign.sprintf("%02s",$hh).':'.sprintf("%02s",$mm).') '.$aTz['timezone_id'];
				if(!empty($key) && !empty($val)){
					$arrResult[$key] = $val;
				}
			}
		}

		return $arrResult;
	}
}

[wheeler]

I couldn't get this to work - for starters I can't extend DateTimeZone (fatal error), and it doesn't seem to be returning any results even though I modified the listAbbreviations line.

I'm thinking i'm just going to create a custom list from windows clock -> timezone or adapt it from something like phpBB registration. Just checked, 5049 time zones in DateTimeZone::listAbbreviations()!

[lampcms.com]

I couldn't get this to work - for starters I can't extend DateTimeZone (fatal error), and it doesn't seem to be returning any results even though I modified the listAbbreviations line.

I'm thinking i'm just going to create a custom list from windows clock -> timezone or adapt it from something like phpBB registration. Just checked, 5049 time zones in DateTimeZone::listAbbreviations()!

That's strange because it worked for me. What php version are you using?

[wheeler]

5.2

[lampcms.com]

OK, I see the problem.
I my own version of this class I don't actually instantiate the extended class and instead using it as a static method



You can also do this, then pass your own array $arrImportantZones to this function

Then the class will look like this:

class clsTZ extends DateTimeZone
{
	
	public function getSelectArray($arrImportantZones){
		$arrResult = array();
		$arr = self::listAbbreviations();

		foreach($arr as $abbr){
			foreach($abbr as $aTz){
				$key = $aTz['timezone_id'];
				if(!in_array($key, $arrImportantZones)){
					continue;
				}
				$sign   = ($aTz['offset'] < 0) ? '-' : ( ($aTz['offset'] > 0) ? '+' : '') ;
				$gmt   = abs($aTz['offset']) / 3600 ;
				$hh     = floor($gmt) ;
				$mm     = $gmt - $hh ;
				$mm  = floor($mm*60) ;

				$val = '(GMT'.$sign.sprintf("%02s",$hh).':'.sprintf("%02s",$mm).') '.$aTz['timezone_id'];
				if(!empty($key) && !empty($val)){
					$arrResult[$key] = $val;
				}
			}
		}

		return $arrResult;
	}
}

$arrTz = clsTZ::getSelectArray($arrImportantZones);

[simshaun]

Download CodeIgniter and open up /system/helpers/date_helper.php

Find function timezones($tz = '') and you'll see an array there.
You could use that array (or the entire date_helper function-set with a little modification.)
A description of that array is at the bottom of the page here.

[wheeler]

thanks, but unfortunately this list is incomplete - I know for sure its missing Australia/Brisbane, which is different from Sydney, Melbourne in that there is no DST. I could obviously add it in but I wonder which other regions might be missing.

Who would've thought this would be so hard! The prospect of hand coding a list is equally unappealing seeing as I need to search the php array for the appropriate time zone name for every zone.

Here is the only method I know of to convert a time:

// Create two timezone objects, one for server and one for user
$utc = new DateTimeZone('UTC');
$user = new DateTimeZone($user_timezone); // looks like Australia/Brisbane or US/Pacific
            
// Create two DateTime objects that will contain the same Unix timestamp, but have different timezones attached to them.
$date_utc = new DateTime('now', $utc);
$date_user = new DateTime('now', $user);
            
$time_offset = $user->getOffset($date_utc); 

[simshaun]

http://en.wikipedia.org/wiki/Time_zone - gives a great overview of it all
http://en.wikipedia.org/wiki/Time_in...lia#Time_zones
http://en.wikipedia.org/wiki/List_of_time_zones
http://wwp.greenwichmeantime.com/info/timezone.htm - i.m.o. - probably the best resource

Useless But Cool:
http://www.timezonecheck.com/

[cranial-bore]

Who would've thought this would be so hard!

Me!
The fact that DST can start and end at different times each year for the same location also makes things complex.

[wheeler]

I'm a bit confused about this page:

http://au.php.net/manual/en/class.datetimezone.php

Is there a way I can return the ALL array which supposedly only contains current time zones (not the backwards compatible ones)?