diff --git a/forms/DateField.php b/forms/DateField.php
index c73953e6b..0a6778ce8 100644
--- a/forms/DateField.php
+++ b/forms/DateField.php
@@ -217,6 +217,8 @@ class DateField extends TextField {
 	 * @param String|Array $val 
 	 */
 	public function setValue($val) {
+		$locale = new Zend_Locale($this->locale);
+		
 		if(empty($val)) {
 			$this->value = null;
 			$this->valueObj = null;
@@ -226,7 +228,7 @@ class DateField extends TextField {
 				if(is_array($val) && $this->validateArrayValue($val)) {
 					// set() gets confused with custom date formats when using array notation
 					if(!(empty($val['day']) || empty($val['month']) || empty($val['year']))) {
-						$this->valueObj = new Zend_Date($val, null, $this->locale);
+						$this->valueObj = new Zend_Date($val, null, $locale);
 						$this->value = $this->valueObj->toArray();
 					} else {
 						$this->value = $val;
@@ -234,8 +236,8 @@ class DateField extends TextField {
 					}
 				}
 				// load ISO date from database (usually through Form->loadDataForm())
-				else if(!empty($val) && Zend_Date::isDate($val, $this->getConfig('datavalueformat'), $this->locale)) {
-					$this->valueObj = new Zend_Date($val, $this->getConfig('datavalueformat'), $this->locale);
+				else if(!empty($val) && Zend_Date::isDate($val, $this->getConfig('datavalueformat'), $locale)) {
+					$this->valueObj = new Zend_Date($val, $this->getConfig('datavalueformat'), $locale);
 					$this->value = $this->valueObj->toArray();
 				}
 				else {
@@ -247,15 +249,15 @@ class DateField extends TextField {
 				// Caution: Its important to have this check *before* the ISO date fallback,
 				// as some dates are falsely detected as ISO by isDate(), e.g. '03/04/03'
 				// (en_NZ for 3rd of April, definetly not yyyy-MM-dd)
-				if(!empty($val) && Zend_Date::isDate($val, $this->getConfig('dateformat'), $this->locale)) {
-					$this->valueObj = new Zend_Date($val, $this->getConfig('dateformat'), $this->locale);
-					$this->value = $this->valueObj->get($this->getConfig('dateformat'), $this->locale);
+				if(!empty($val) && Zend_Date::isDate($val, $this->getConfig('dateformat'), $locale)) {
+					$this->valueObj = new Zend_Date($val, $this->getConfig('dateformat'), $locale);
+					$this->value = $this->valueObj->get($this->getConfig('dateformat'), $locale);
 					
 				}
 				// load ISO date from database (usually through Form->loadDataForm())
 				else if(!empty($val) && Zend_Date::isDate($val, $this->getConfig('datavalueformat'))) {
 					$this->valueObj = new Zend_Date($val, $this->getConfig('datavalueformat'));
-					$this->value = $this->valueObj->get($this->getConfig('dateformat'), $this->locale);
+					$this->value = $this->valueObj->get($this->getConfig('dateformat'), $locale);
 				}
 				else {
 					$this->value = $val;
diff --git a/forms/DatetimeField.php b/forms/DatetimeField.php
index 4d768a87e..20b84eb79 100644
--- a/forms/DatetimeField.php
+++ b/forms/DatetimeField.php
@@ -115,6 +115,8 @@ class DatetimeField extends FormField {
 	 *  the 'date' value may contain array notation was well (see {@link DateField->setValue()}).
 	 */
 	public function setValue($val) {
+		$locale = new Zend_Locale($this->locale);
+
 		// If timezones are enabled, assume user data needs to be reverted to server timezone
 		if($this->getConfig('usertimezone')) {
 			// Accept user input on timezone, but only when timezone support is enabled
@@ -130,7 +132,7 @@ class DatetimeField extends FormField {
 			$this->timeField->setValue(null);
 		} else {
 			// Case 1: String setting from database, in ISO date format
-			if(is_string($val) && Zend_Date::isDate($val, $this->getConfig('datavalueformat'), $this->locale)) {
+			if(is_string($val) && Zend_Date::isDate($val, $this->getConfig('datavalueformat'), $locale)) {
 				$this->value = $val;
 			}
 			// Case 2: Array form submission with user date format
@@ -145,13 +147,13 @@ class DatetimeField extends FormField {
 				$this->dateField->setValue($val['date']);
 				$this->timeField->setValue($val['time']);
 				if($this->dateField->dataValue() && $this->timeField->dataValue()) {
-					$userValueObj = new Zend_Date(null, null, $this->locale);
+					$userValueObj = new Zend_Date(null, null, $locale);
 					$userValueObj->setDate($this->dateField->dataValue(),
 						$this->dateField->getConfig('datavalueformat'));
 					$userValueObj->setTime($this->timeField->dataValue(),
 						$this->timeField->getConfig('datavalueformat'));
 					if($userTz) $userValueObj->setTimezone($dataTz);
-					$this->value = $userValueObj->get($this->getConfig('datavalueformat'), $this->locale);
+					$this->value = $userValueObj->get($this->getConfig('datavalueformat'), $locale);
 					unset($userValueObj);
 				} else {
 					// Validation happens later, so set the raw string in case Zend_Date doesn't accept it
@@ -168,8 +170,8 @@ class DatetimeField extends FormField {
 			}
 
 			// view settings (dates might differ from $this->value based on user timezone settings)
-			if (Zend_Date::isDate($this->value, $this->getConfig('datavalueformat'), $this->locale)) {
-				$valueObj = new Zend_Date($this->value, $this->getConfig('datavalueformat'), $this->locale);
+			if (Zend_Date::isDate($this->value, $this->getConfig('datavalueformat'), $locale)) {
+				$valueObj = new Zend_Date($this->value, $this->getConfig('datavalueformat'), $locale);
 				if($userTz) $valueObj->setTimezone($userTz);
 
 				// Set view values in sub-fields
@@ -177,9 +179,9 @@ class DatetimeField extends FormField {
 					$this->dateField->setValue($valueObj->toArray());
 				} else {
 					$this->dateField->setValue(
-						$valueObj->get($this->dateField->getConfig('dateformat'), $this->locale));
+						$valueObj->get($this->dateField->getConfig('dateformat'), $locale));
 				}
-				$this->timeField->setValue($valueObj->get($this->timeField->getConfig('timeformat'), $this->locale));
+				$this->timeField->setValue($valueObj->get($this->timeField->getConfig('timeformat'), $locale));
 			}
 		}
 
diff --git a/i18n/i18n.php b/i18n/i18n.php
index fd87f58fa..ff848ba3f 100644
--- a/i18n/i18n.php
+++ b/i18n/i18n.php
@@ -2231,13 +2231,11 @@ class i18n extends Object implements TemplateGlobalProvider {
 					// TODO Replace with CLDR list of actually available languages/regions
 					// Only allow explicitly registered locales, otherwise we'll get into trouble
 					// if the locale doesn't exist in Zend's CLDR data
-					$labelLocale = str_replace('-', '_', self::get_locale_from_lang($locale));
-					if(isset(self::$all_locales[$locale])) {
-						$locales[$locale] = self::$all_locales[$locale];	
-					} else if(isset(self::$all_locales[$labelLocale])) {
-						$locales[$locale] = self::$all_locales[$labelLocale];	
-					} 
-				} 
+					$fullLocale = self::get_locale_from_lang($locale);
+					if(isset($allLocales[$fullLocale])) {
+						$locales[$fullLocale] = $allLocales[$fullLocale];	
+					}
+				}
 			}
 		}
 
@@ -2354,7 +2352,7 @@ class i18n extends Object implements TemplateGlobalProvider {
 	public static function get_locale_from_lang($lang) {
 		$subtags = Config::inst()->get('i18n', 'likely_subtags');
 		if(preg_match('/\-|_/', $lang)) {
-			return $lang;
+			return str_replace('-', '_', $lang);
 		} else if(isset($subtags[$lang])) {
 			return $subtags[$lang];
 		} else {
diff --git a/security/Member.php b/security/Member.php
index 051c6798d..07defd2a6 100644
--- a/security/Member.php
+++ b/security/Member.php
@@ -1169,7 +1169,7 @@ class Member extends DataObject implements TemplateGlobalProvider {
 		$password->setCanBeEmpty(true);
 		if(!$this->ID) $password->showOnClick = false;
 		$mainFields->replaceField('Password', $password);
-				
+
 		$mainFields->replaceField('Locale', new DropdownField(
 			"Locale", 
 			_t('Member.INTERFACELANG', "Interface Language", 'Language of the CMS'), 
@@ -1231,7 +1231,7 @@ class Member extends DataObject implements TemplateGlobalProvider {
 		$permissionsTab = $fields->fieldByName("Root")->fieldByName('Permissions');
 		if($permissionsTab) $permissionsTab->addExtraClass('readonly');
 		
-		$defaultDateFormat = Zend_Locale_Format::getDateFormat($this->Locale);
+		$defaultDateFormat = Zend_Locale_Format::getDateFormat(new Zend_Locale($this->Locale));
 		$dateFormatMap = array(
 			'MMM d, yyyy' => Zend_Date::now()->toString('MMM d, yyyy'),
 			'yyyy/MM/dd' => Zend_Date::now()->toString('yyyy/MM/dd'),
@@ -1249,7 +1249,7 @@ class Member extends DataObject implements TemplateGlobalProvider {
 		);
 		$dateFormatField->setValue($this->DateFormat);
 		
-		$defaultTimeFormat = Zend_Locale_Format::getTimeFormat($this->Locale);
+		$defaultTimeFormat = Zend_Locale_Format::getTimeFormat(new Zend_Locale($this->Locale));
 		$timeFormatMap = array(
 			'h:mm a' => Zend_Date::now()->toString('h:mm a'),
 			'H:mm' => Zend_Date::now()->toString('H:mm'),
diff --git a/tests/i18n/i18nTest.php b/tests/i18n/i18nTest.php
index ee5f2dd27..0e5af4adb 100644
--- a/tests/i18n/i18nTest.php
+++ b/tests/i18n/i18nTest.php
@@ -97,9 +97,9 @@ class i18nTest extends SapphireTest {
 	
 	public function testGetExistingTranslations() {
 		$translations = i18n::get_existing_translations();
-		$this->assertTrue(isset($translations['en']), 'Checking for en translation');
-		$this->assertEquals($translations['en'], 'English (United States)');
-		$this->assertTrue(isset($translations['de']), 'Checking for de_DE translation');
+		$this->assertTrue(isset($translations['en_US']), 'Checking for en translation');
+		$this->assertEquals($translations['en_US'], 'English (United States)');
+		$this->assertTrue(isset($translations['de_DE']), 'Checking for de_DE translation');
 	}
 	
 	public function testDataObjectFieldLabels() {