Fix timezone initialization in core.php

Prior to this, core.php would trigger a PHP warning on PHP >= 5.3 when
date_default_timezone_get() is not able to determine the timezone and
defaults to UTC (e.g. when php.ini date.timezone is not set).

The timezone is determined in the following order
  1. user preferences
  2. MantisBT configuration ($g_default_timezone)
  3. php.ini setting (date.timezone)
  4. UTC (set by date_default_timezone_get())

Fixes #17747

core.php

@@ -236,33 +236,27 @@ function __autoload( $p_class ) {
 	$g_login_anonymous = true;
 }
 
-# Attempt to set the current timezone to the user's desired value
-# Note that PHP 5.1 on RHEL/CentOS doesn't support the timezone functions
-# used here so we just skip this action on RHEL/CentOS platforms.
-if( function_exists( 'timezone_identifiers_list' ) ) {
-	if( in_array( config_get_global( 'default_timezone' ), timezone_identifiers_list() ) ) {
-		# if a default timezone is set in config, set it here, else we use php.ini's value
-		# having a timezone set avoids a php warning
-		date_default_timezone_set( config_get_global( 'default_timezone' ) );
-	} else {
-		# To ensure proper detection of timezone settings issues, we must not
-		# initialize the default timezone when executing admin checks
-		if( basename( $g_short_path ) != 'check' ) {
-			config_set_global( 'default_timezone', date_default_timezone_get(), true );
-		}
-	}
-
+# Set the current timezone
+if( !defined( 'MANTIS_MAINTENANCE_MODE' ) ) {
 	require_api( 'authentication_api.php' );
+
+	# To reduce overhead, we assume that the timezone configuration is valid,
+	# i.e. it exists in timezone_identifiers_list(). If not, a PHP NOTICE will
+	# be raised. Use admin checks to validate configuration.
+	@date_default_timezone_set( config_get_global( 'default_timezone' ) );
+	$t_tz = @date_default_timezone_get();
+	config_set_global( 'default_timezone', $t_tz, true );
+
 	if( auth_is_user_authenticated() ) {
+		# Determine the current timezone according to user's preferences
 		require_api( 'user_pref_api.php' );
-
-		$t_user_timezone = user_pref_get_pref( auth_get_current_user_id(), 'timezone' );
-		if( !is_blank( $t_user_timezone ) ) {
-			date_default_timezone_set( $t_user_timezone );
-		}
+		$t_tz = user_pref_get_pref( auth_get_current_user_id(), 'timezone' );
+		@date_default_timezone_set( $t_tz );
 	}
+	unset( $t_tz );
 }
 
+# Cache current user's collapse API data
 if( !defined( 'MANTIS_MAINTENANCE_MODE' ) ) {
 	require_api( 'collapse_api.php' );
 	collapse_cache_token();

core/date_api.php

@@ -23,18 +23,22 @@
  * @copyright Copyright 2002  MantisBT Team - mantisbt-dev@lists.sourceforge.net
  * @link http://www.mantisbt.org
  *
+ * @uses authentication_api.php
  * @uses config_api.php
  * @uses constant_inc.php
  * @uses helper_api.php
  * @uses html_api.php
  * @uses lang_api.php
+ * @uses user_pref_api.php
  */
 
+require_api( 'authentication_api.php' );
 require_api( 'config_api.php' );
 require_api( 'constant_inc.php' );
 require_api( 'helper_api.php' );
 require_api( 'html_api.php' );
 require_api( 'lang_api.php' );
+require_api( 'user_pref_api.php' );
 
 # Keeps track of whether the external files required for jscalendar to work
 # have already been included in the output sent to the client. jscalendar