date_default_timezone_set

(PHP 5 >= 5.1.0, PHP 7)

date_default_timezone_set — 设定用于一个脚本中所有日期时间函数的默认时区

说明

bool date_default_timezone_set ( string $timezone_identifier )

date_default_timezone_set() 设定用于所有日期时间函数的默认时区。

Note:

自 PHP 5.1.0 起（此版本日期时间函数被重写了），如果时区不合法则每个对日期时间函数的调用都会产生一条 E_NOTICE 级别的错误信息，如果使用系统设定或 TZ 环境变量则还会产生 E_STRICT 级别的信息。

除了用此函数，你还可以通过 INI 设置 date.timezone 来设置默认时区。

参数

timezone_identifier

时区标识符，例如 UTC 或 Europe/Lisbon。合法标识符列表见所支持的时区列表。

返回值

如果 timezone_identifier 参数无效则返回 FALSE，否则返回 TRUE。

范例

Example #1 获取默认时区

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

$script_tz = date_default_timezone_get();

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

更新日志

版本 说明
5.3.0 现在会抛出 E_WARNING 而不是 E_STRICT。
5.1.2 本版本开始验证 timezone_identifier 参数。

参见

User Contributed Notes

Lance E Sloan 27-Oct-2017 11:05
I avoid using strings as arguments when a constant or other kind of reference should be used.  For example, to set the default timezone to UTC, the recommended code is:

<?php
date_default_timezone_set('UTC'); // Potential for mistakes
?>

However, using the string "UTC" here opens up the possibility for mistakes.  For example, if the string "UTX" were entered accidentally,
most PHP editors PHP won't flag that as an error.  When run, the interpreter will show the common warning about a misspelled timezone and using "UTC" by default. 

PHP should define constants to represent the major timezones.  Actually it does, but "DateTimeZone::UTC" inconveniently contains the integer value 1024, not a string.  However, "DateTimeZone::listIdentifiers()" can turn a timezone integer into an array of timezone identifier strings.  So, I use this code:

<?php
date_default_timezone_set(DateTimeZone::listIdentifiers(DateTimeZone::UTC)[0]);  // Foolproof
?>

It's longer, but if I make a mistake specifying the timezone (which I won't because I use code completion), my editor would highlight the problem. If I ran the program with an invalid timezone reference anyway, PHP would give the more helpful error, "Fatal error: Undefined class constant 'UTX' in /tmp/tarfu.php on line 24".
Jesse dot Chisholm at gmail dot com 19-Apr-2015 09:10
I found a need to change the timezone based on a DB record, so it would display properly for each record.  So I wrapped some of the other posts into this small class:

<?php
class TZStack
{
    private $stack = array();
    public function __construct(){}
    public function push($newTZ)
    {
        array_push($this->stack, date_default_timezone_get());
        if (isset($newTZ) && ("" != $newTZ))
        {
            date_default_timezone_set($newTZ);
        }
    }
    public function pop()
    {
        if (count($this->stack) > 0)
        {
            date_default_timezone_set(array_pop($this->stack));
        }
    }
}
// the global TZ stack for the rest of the code  to use.
$tzStack = new TZStack();
// In case I need to know the TZ at the web server. :)
$script_tz = date_default_timezone_get();
?>

Then in my per-record code:

<?php
    foreach($records as $item)
    {
        $tzStack->push($item['TZ']);
        $TZ = date("T", time());
        // code that displays this record, using $TZ.
        $tzStack->pop();
    }
?>
Anteaus 02-Jan-2015 09:04
This creates a huge problem for downloadable programs, which obviously cannot be hardcoded as this suggests, since the coder has no idea where they will be run.

Seems to me that if the server's timezone cannot be relied on, then THAT is the the problem which needs fixed. Not, cause the coder's syntactically-correct work to generate bogus error messages.
Taylor 31-May-2014 06:47
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.
chris at clwill dot com 11-Dec-2013 08:54
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.
Christopher Kramer 10-Mar-2013 06:39
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.)
Pierre Gourlaouen 06-Jul-2012 05:45
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
?>
daneiracleous at gmail dot com 28-Jan-2012 05:11
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
?>
power2all at gmail dot com 01-Feb-2011 05:30
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"));
}
?>
Anonymous 20-Nov-2010 10:58
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
steve at pozzie dot net 11-Oct-2010 10:35
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;
 }
?>
Tom S 11-Sep-2010 03:22
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);
Frederick Hathaway 04-Mar-2010 05:54
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;
    }
?>
Christopher Kramer 09-Jan-2010 04:52
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.
ted dot chou12 at gmail dot com 03-Dec-2008 08:13
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|
jason at jasonpriem dot com 12-Nov-2008 05:29
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]
Rob Kaper 15-Jul-2008 10:46
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 );

?>
PeerGoal.com 12-Feb-2007 01:21
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");
davidn at datalinktech dot com dot au 22-Dec-2006 02:27
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.