PHP 5.4.32 Released

date_default_timezone_set

(PHP 5 >= 5.1.0)

date_default_timezone_set Sets the default timezone used by all date/time functions in a script

Description

bool date_default_timezone_set ( string $timezone_identifier )

date_default_timezone_set() sets the default timezone used by all date/time functions.

Note:

Since PHP 5.1.0 (when the date/time functions were rewritten), every call to a date/time function will generate a E_NOTICE if the timezone isn't valid, and/or a E_WARNING message if using the system settings or the TZ environment variable.

Instead of using this function to set the default timezone in your script, you can also use the INI setting date.timezone to set the default timezone.

Parameters

timezone_identifier

The timezone identifier, like UTC or Europe/Lisbon. The list of valid identifiers is available in the List of Supported Timezones.

Return Values

This function returns FALSE if the timezone_identifier isn't valid, or TRUE otherwise.

Examples

Example #1 Getting the default timezone

<?php
date_default_timezone_set
('America/Los_Angeles');

$script_tz date_default_timezone_get();

if (
strcmp($script_tzini_get('date.timezone'))){
    echo 
'Script timezone differs from ini-set timezone.';
} else {
    echo 
'Script timezone and ini-set timezone match.';
}
?>

Changelog

Version Description
5.3.0 Now throws E_WARNING rather than E_STRICT.
5.1.2 The function started to validate the timezone_identifier parameter.

See Also

add a note add a note

User Contributed Notes 17 notes

up
4
Christopher Kramer
4 years ago
I experienced that using this function highly increases performance of functions like getdate() or date() using PHP 5.2.6 on Windows.
I experienced similar results on Linux servers with PHP 5.2.6 and 5.2.10, although the difference was not that significant on these servers: The PHP 5.2.10 server did run with date_default_timezone_set ("only") twice as fast as without. The 5.2.6 server did 5 times faster with date_default_timezone_set. As you can see below, the 5.2.6-Windows machine did a LOT faster.
Of course these machines have completely different hardware and can not really be compared, but all show improved performance.

I checked PHP 4.4.9 on Windows (without date_default_timezone_set of course) and noticed that its as fast as PHP 5.2.6 with date_default_timezone_set.

The following script shows this:

<?php

# uncomment to see difference
# date_default_timezone_set(date_default_timezone_get());

function getmicrotime()
{
list(
$usec, $sec) = explode(' ',microtime());
return (
$sec.substr($usec,1,7));
}

$start=mktime(0,0,0,1,1,2005);
$end=mktime(0,0,0,1,1,2020);
$nr=50000;

$start_time=getmicrotime();
for(
$i=0;$i<$nr;$i++) {
# $value=getdate(rand($start,$end));
 
date("H:i:s d.m.Y",rand($start,$end));
}
$end_time=getmicrotime();

echo
"Time: ".($end_time-$start_time);

// With date_default_timezone_set(): "Time: 0.379343986511"
// Without date_default_timezone_set(): "Time: 7.4971370697"

?>

Note that the timezone is not changed, it is only set again. I really wonder why this makes such a big performance difference, but its good to know.
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2
chris at clwill dot com
8 months ago
I'm sure I'm not the only one who is distressed by the recent default behavior change to E_NOTICE when the timezone isn't explicitly set in the program or in .ini.  I insure that the clock on the server IS correct, and I don't want to have to set it in two places (the system AND PHP).  So I want to read it from the system.  But PHP won't accept that answer, and insists on a call to this function.  So, here's my answer:

<?php
function setTimezone($default) {
   
$timezone = "";
   
   
// On many systems (Mac, for instance) "/etc/localtime" is a symlink
    // to the file with the timezone info
   
if (is_link("/etc/localtime")) {
       
       
// If it is, that file's name is actually the "Olsen" format timezone
       
$filename = readlink("/etc/localtime");
       
       
$pos = strpos($filename, "zoneinfo");
        if (
$pos) {
           
// When it is, it's in the "/usr/share/zoneinfo/" folder
           
$timezone = substr($filename, $pos + strlen("zoneinfo/"));
        } else {
           
// If not, bail
           
$timezone = $default;
        }
    }
    else {
       
// On other systems, like Ubuntu, there's file with the Olsen time
        // right inside it.
       
$timezone = file_get_contents("/etc/timezone");
        if (!
strlen($timezone)) {
           
$timezone = $default;
        }
    }
   
date_default_timezone_set($timezone);
}
?>

Use it by calling it with a fallback default answer.

Yes, I know it doesn't work on Windows.  Neither do I :)  Perhaps someone wants to add that functionality.

Hope this helps someone.
up
3
PeerGoal.com
7 years ago
The problem:

date() [function.date]: It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'America/Los_Angeles' for 'PST/-8.0/no DST' instead

Of course this is a problem that recently surfaced since PHP5. Quick fix is to set your time zone, add this line to your php code:

date_default_timezone_set("America/Los_Angeles");
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2
steve at pozzie dot net
3 years ago
Most of the scripts here depend on PHP identifying the correct zone when one is not set, but that does not always happen.

For example PHP 5.3.3 gives a 'UTC' result for a detected '8.0/no DST'. Not much help.

So for those of us who for very good reasons really cannot set time zones in scripts of in .ini files, here is a function
for use in a Windows environment that sets the default time zone to the OS time zone and returns the detected and set texts.

<?php
function date_system_timezone_set(){
 
$shell = new COM("WScript.Shell") or die("Requires Windows Scripting Host");
 
$time_bias = -($shell->RegRead(
"HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Control
\\TimeZoneInformation\\Bias"
))/60;
 
$ab = -($shell->RegRead(
"HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Control
\\TimeZoneInformation\\ActiveTimeBias"
))/60;
 
$sc = $shell->RegRead(
"HKEY_USERS\\.DEFAULT\\Control Panel\\International\\sCountry");
  foreach(
timezone_abbreviations_list() as $tza) foreach($tza as $entry){
   
$country = strtok($entry['timezone_id'],'/');
   
$locale = strtok('|');
    if(
$country==$sc && $ab==($entry['offset']/60/60) && ($ds = $time_bias!=$ab)==$entry['dst']){
     
date_default_timezone_set($timezone_identifier = $country."/".$locale);
      return
sprintf('%.1f',$ab)."/".($ds?'':'no ').'DST'." ".$timezone_identifier;
     }
   }
  return
false;
}
?>
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1
Frederick Hathaway
4 years ago
It's really a hassle that there is no way to set the timezone offset. I attempted to use the code that searched for the correct timezone name by offset from below. I found it didn't work reliably since various cities may have different rules about time DST etc. My solution is to actually search the array and do a test to insure the offset is what I expect it to be. It seems very kludgey (if thats a word) but it works.

<?php
function setTimezoneByOffset($offset)
    {
     
$testTimestamp = time();
       
date_default_timezone_set('UTC');
       
$testLocaltime = localtime($testTimestamp,true);
       
$testHour = $testLocaltime['tm_hour'];       

     
   
$abbrarray = timezone_abbreviations_list();
    foreach (
$abbrarray as $abbr)
    {
       
//echo $abbr."<br>";
     
foreach ($abbr as $city)
      {
               
date_default_timezone_set($city['timezone_id']);
               
$testLocaltime     = localtime($testTimestamp,true);
               
$hour                     = $testLocaltime['tm_hour'];       
               
$testOffset $hour - $testHour;
                if(
$testOffset == $offset)
                {
                    return
true;
                }
      }
    }
    return
false;
    }
?>
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1
Rob Kaper
6 years ago
If you want users to choose their own timezones, here's some code that gets all available timezones but only uses one city for each possible value:

<?php

$timezones
= DateTimeZone::listAbbreviations();

$cities = array();
foreach(
$timezones as $key => $zones )
{
    foreach(
$zones as $id => $zone )
    {
       
/**
         * Only get timezones explicitely not part of "Others".
         * @see http://www.php.net/manual/en/timezones.others.php
         */
       
if ( preg_match( '/^(America|Antartica|Arctic|Asia|Atlantic|Europe|Indian|Pacific)\//', $zone['timezone_id'] ) )
           
$cities[$zone['timezone_id']][] = $key;
    }
}

// For each city, have a comma separated list of all possible timezones for that city.
foreach( $cities as $key => $value )
   
$cities[$key] = join( ', ', $value);

// Only keep one city (the first and also most important) for each set of possibilities.
$cities = array_unique( $cities );

// Sort by area/city name.
ksort( $cities );

?>
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0
okhugo at gmail dot com
1 hour ago
Get the difference between current timezone and UTC/GMT
<?php
function dif_hora(){
   
$zona_s= date('P');
   
$t=explode(":",$zona_s);
   
$horas=($t[0])*1;
   
$sale['horas']=$horas;
   
$sale['min']=$horas*60;
   
$sale['seg']=$horas*60*60;
    return
$sale;
    }
print_r (dif_hora());

// Changing default server zone America/New_York
ini_set('date.timezone','America/Costa_Rica');

print_r (dif_hora());
?>

result:
Array
(
    [horas] => -4
    [min] => -240
    [seg] => -14400
)
Array
(
    [horas] => -6
    [min] => -360
    [seg] => -21600
)
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0
Taylor
2 months ago
I was having major issues with the date.timezone setting after I updated from 5.3.3 to 5.4.29. I still need to update further, and perhaps it's a bug in this version that will be fixed when I update..

But to fix the issue of php not being about to find my time zone, I added a .htaccess file to the root of my web directory. All I have in it is this one line (without quotes)

"php_value date.timezone America/Denver"

And now the timezone is set in any directory I browse in. Very strange, and I still haven't figured out why It wont work from the php.ini file. But here's how to overcome the frustration.
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0
Pierre Gourlaouen
2 years ago
A simple method for conversation between two time zone.

<?php
$date
= new DateTime("2012-07-05 16:43:21", new DateTimeZone('Europe/Paris'));

date_default_timezone_set('America/New_York');

echo
date("Y-m-d h:iA", $date->format('U'));

// 2012-07-05 10:43AM
?>
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-1
power2all at gmail dot com
3 years ago
After poundering and knocking my head on the table, I finally got a proper fix for Windows and PHP timezone handling.

Since Windows applies the DST to ActiveTimeBias in the registry, you only need this to apply.
The only problem is, that it cant use the timezone_set command.

You can request a response back in any date-format you wish, or use the default one given in the function itself.

<?php

// Return proper time
function time_zone_fix($timeGiven = "H:i:s")
{
   
$shell = new COM("WScript.Shell") or die("Requires Windows Scripting Host");
   
$time_bias = -($shell->RegRead("HKEY_LOCAL_MACHINE\\SYSTEM\\
CurrentControlSet\\Control\\TimeZoneInformation\\
ActiveTimeBias"
)) / 60;
   
$timestamp_bias = 60 * 60 * $time_bias;
    echo
$time_bias . "<br />";
    return
gmdate($timeGiven, strtotime($timestamp_bias . " seconds"));
}
?>
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-3
Christopher Kramer
1 year ago
Regarding my post 3 years before:
The performance impact seems to be caused by the fact that a log message is written if you do not set a timezone. And writing a log message to disk can take significantly longer than actually calculating date() or getdate() - esp. on systems with slow IO like the Windows machine I used 3 years ago.

PHP 4 did not produce any log messages, and therefore was as fast as PHP5 with a timezone set.

So if you run date() or getdate() a lot of times, this will cause a lot of log messages to be written to disk (if you did not disable them in your php.ini settings), which will take its time.

So either use this function or set the ini-setting "date.timezone" to make things faster.
(And have a look into your logfiles! Solving all those warnings will not only save you disk space but will also speed up your web application.)
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-3
Tom S
3 years ago
This is a good script if you know or control your system so that you know that the local TZ in your OS is correct. Unfortunately, this script still creates an warning message under BSD UNIX.

To fix this, just add an "@" in front of "localtime" as:

$arr = @localtime($iTime);
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-2
davidn at datalinktech dot com dot au
7 years ago
Note that there may be some unexpected side-effects that result from using either set_default_timezone() or the putenv("TZ=...") workalike for earlier PHP versions.  ANY date formatted and output either by PHP or its apache host process will be unconditionally expressed in that timezone.

[red. That is only true for the putenv() hack - Derick]

This does indeed include the web server's logs and other output files and reports which by default usually do not include any indication of timezone. This has a further side-effect on log processing and analysis, obviously.
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-4
Anonymous
3 years ago
People complaining that there's no way to set the offset - you are wrong. You can easily set the offset from GMT (see "Other" in available zones). And since all zones are offset from GMT it's just easy math with + or - to get that. So if you i.e. want the offset not from GMT but your timezone, then compute offset of your zone from GMT (say if you in Berlin its +1 now (mind summer time!)) and then offset for your target zone (i.e NYC is -5) then sum abs! of these values and set the sign of bigger (abs) value -> total offset from your european zone to NYC is then abs(-5)+abs(1) = 6 and set "-" as NYC zone absolute value is bigger. So whatever time is in Berlin, in NYC it's 6hrs earlier. But it's better to do two step calculation and calculate always from GMT
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-5
jason at jasonpriem dot com
5 years ago
While it's easy to change timezones based on names or abbreviations, I haven't found any straightforward way of doing so using an offset integer.  This situation comes up if you're using AJAX to get information about a user's timezone; javascript's getTimezoneOffset() method just sends you an offset number. So, here's my clunky solution: an adaptation of chris' function at http://us.php.net/manual/en/function.timezone-name-from-abbr.php.

<?php
   
function set_tz_by_offset($offset) {
       
$offset = $offset*60*60;
       
$abbrarray = timezone_abbreviations_list();
        foreach (
$abbrarray as $abbr) {
           
//echo $abbr."<br>";
               
foreach ($abbr as $city) {
                   
//echo $city['offset']." $offset<br>";
                       
if ($city['offset'] == $offset) { // remember to multiply $offset by -1 if you're getting it from js
                              
date_default_timezone_set($city['timezone_id']);
                               return
true;
                        }
                }
        }
   
date_default_timezone_set("ust");
       return
false;
       }

set_tz_by_offset(-1);

?>

[EDIT BY thiago AT php DOT net: This code has contributions from iateadonut at gmail dot com]
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-9
daneiracleous at gmail dot com
2 years ago
If you want to set the default timezone to the user's local timezone, you have to combine PHP and JavaScript. Here's how to do it:

<?php
session_start
();
if(!isset(
$_SESSION['timezone']))
{
    if(!isset(
$_REQUEST['offset']))
    {
   
?>
    <script>
    var d = new Date()
    var offset= -d.getTimezoneOffset()/60;
    location.href = "<?php echo $_SERVER['PHP_SELF']; ?>?offset="+offset;
    </script>
    <?php   
   
}
    else
    {
       
$zonelist = array('Kwajalein' => -12.00, 'Pacific/Midway' => -11.00, 'Pacific/Honolulu' => -10.00, 'America/Anchorage' => -9.00, 'America/Los_Angeles' => -8.00, 'America/Denver' => -7.00, 'America/Tegucigalpa' => -6.00, 'America/New_York' => -5.00, 'America/Caracas' => -4.30, 'America/Halifax' => -4.00, 'America/St_Johns' => -3.30, 'America/Argentina/Buenos_Aires' => -3.00, 'America/Sao_Paulo' => -3.00, 'Atlantic/South_Georgia' => -2.00, 'Atlantic/Azores' => -1.00, 'Europe/Dublin' => 0, 'Europe/Belgrade' => 1.00, 'Europe/Minsk' => 2.00, 'Asia/Kuwait' => 3.00, 'Asia/Tehran' => 3.30, 'Asia/Muscat' => 4.00, 'Asia/Yekaterinburg' => 5.00, 'Asia/Kolkata' => 5.30, 'Asia/Katmandu' => 5.45, 'Asia/Dhaka' => 6.00, 'Asia/Rangoon' => 6.30, 'Asia/Krasnoyarsk' => 7.00, 'Asia/Brunei' => 8.00, 'Asia/Seoul' => 9.00, 'Australia/Darwin' => 9.30, 'Australia/Canberra' => 10.00, 'Asia/Magadan' => 11.00, 'Pacific/Fiji' => 12.00, 'Pacific/Tongatapu' => 13.00);
       
$index = array_keys($zonelist, $_REQUEST['offset']);
       
$_SESSION['timezone'] = $index[0];
    }
}
date_default_timezone_set($_SESSION['timezone']);

//rest of your code goes here
?>
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-9
ted dot chou12 at gmail dot com
5 years ago
Timezone using other approaches:
<?php $datetime = strtotime($originaldatetime) + $time;
$datetime = date('M d, Y h:i A', $datetime);?>

$time obtained from table below:
-25200|International Date Line (West) GMT-12|
-21600|Midway Island, Samoa GMT-11|
-18000|Hawaii, Honolulu GMT-10|
-14400|Alaska GMT-9|
-10800|Pacific Standard Time, US, Canada GMT-8|
-7200|British Columbia N.E., Santa Fe, Mountain Time GMT-7|
-3600|Central America, Chicago, Guatamala, Mexico City GMT-6|
0|US, Canada, Bogota, Boston, New York GMT-5|
+3600|Canada, Santiago, Atlantic Standard Time GMT-4|
+7200|Brazilia, Buenos Aires, Georgetown, Greenland GMT-3|
+10800|Mid-Atlantic GMT-2|
+14400|Azores, Cape Verde Is., Western Africa Time GMT-1|
+18000|London, Iceland, Ireland, Morocco, Portugal GMT|
+21600|Amsterdam, Berlin, Bern, Madrid, Paris, Rome, GMT+1|
+25200|Athens, Cairo, Cape Town, Finland, Greece, Israel GMT+2|
+28800|Ankara, Aden, Baghdad, Beruit, Kuwait, Moscow GMT+3|
+32400|Abu Dhabi, Baku, Kabul, Tehran, Tbilisi, Volgograd GMT+4|
+36000|Calcutta, Colombo, Islamabad, Madras, New Dehli GMT+5|
+39600|Almaty, Dhakar, Kathmandu, Colombo, Sri Lanka GMT+6|
+43200|Bangkok, Hanoi, Jakarta, Phnom Penh, Australia GMT+7|
+46800|Taipei, Beijing, Hong Kong, Singapore, GMT+8|
+50400|Seoul, Tokyo, Central Australia GMT+9|
+54000|Brisbane, Canberra, Guam, Melbourne, Sydney, GMT+10|
+57600|Magadan, New Caledonia, Solomon Is. GMT+11|
+61200|Auckland, Fiji, Kamchatka, Marshall, Wellington, GMT+12|
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