diff --git a/apps/theming/lib/Controller/ThemingController.php b/apps/theming/lib/Controller/ThemingController.php
index 6c87315a2e..24865cc2c6 100644
--- a/apps/theming/lib/Controller/ThemingController.php
+++ b/apps/theming/lib/Controller/ThemingController.php
@@ -33,6 +33,7 @@ use OCP\AppFramework\Http;
 use OCP\AppFramework\Http\DataDownloadResponse;
 use OCP\AppFramework\Http\DataResponse;
 use OCP\AppFramework\Http\StreamResponse;
+use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\Files\IRootFolder;
 use OCP\IConfig;
 use OCP\IL10N;
@@ -49,6 +50,10 @@ use OCA\Theming\Util;
 class ThemingController extends Controller {
 	/** @var Template */
 	private $template;
+	/** @var Util */
+	private $util;
+	/** @var ITimeFactory */
+	private $timeFactory;
 	/** @var IL10N */
 	private $l;
 	/** @var IConfig */
@@ -63,6 +68,8 @@ class ThemingController extends Controller {
 	 * @param IRequest $request
 	 * @param IConfig $config
 	 * @param Template $template
+	 * @param Util $util
+	 * @param ITimeFactory $timeFactory
 	 * @param IL10N $l
 	 * @param IRootFolder $rootFolder
 	 */
@@ -71,12 +78,16 @@ class ThemingController extends Controller {
 		IRequest $request,
 		IConfig $config,
 		Template $template,
+		Util $util,
+		ITimeFactory $timeFactory,
 		IL10N $l,
 		IRootFolder $rootFolder
 	) {
 		parent::__construct($appName, $request);
 
 		$this->template = $template;
+		$this->util = $util;
+		$this->timeFactory = $timeFactory;
 		$this->l = $l;
 		$this->config = $config;
 		$this->rootFolder = $rootFolder;
@@ -178,7 +189,7 @@ class ThemingController extends Controller {
 
 		$response = new Http\StreamResponse($pathToLogo);
 		$response->cacheFor(3600);
-		$response->addHeader('Expires', date(\DateTime::RFC2822));
+		$response->addHeader('Expires', date(\DateTime::RFC2822, $this->timeFactory->getTime()));
 		$response->addHeader('Content-Disposition', 'attachment');
 		$response->addHeader('Content-Type', $this->config->getAppValue($this->appName, 'logoMime', ''));
 		return $response;
@@ -198,7 +209,7 @@ class ThemingController extends Controller {
 
 		$response = new StreamResponse($pathToLogo);
 		$response->cacheFor(3600);
-		$response->addHeader('Expires', date(\DateTime::RFC2822));
+		$response->addHeader('Expires', date(\DateTime::RFC2822, $this->timeFactory->getTime()));
 		$response->addHeader('Content-Disposition', 'attachment');
 		$response->addHeader('Content-Type', $this->config->getAppValue($this->appName, 'backgroundMime', ''));
 		return $response;
@@ -214,7 +225,7 @@ class ThemingController extends Controller {
 		$cacheBusterValue = $this->config->getAppValue('theming', 'cachebuster', '0');
 		$responseCss = '';
 		$color = $this->config->getAppValue($this->appName, 'color');
-		$elementColor = Util::elementColor($color);
+		$elementColor = $this->util->elementColor($color);
 		if($color !== '') {
 			$responseCss .= sprintf(
 				'#body-user #header,#body-settings #header,#body-public #header,#body-login,.searchbox input[type="search"]:focus,.searchbox input[type="search"]:active,.searchbox input[type="search"]:valid {background-color: %s}' . "\n",
@@ -229,7 +240,7 @@ class ThemingController extends Controller {
 				$elementColor
 			);
 			$responseCss .= 'input[type="radio"].radio:checked:not(.radio--white):not(:disabled) + label:before {' .
-				'background-image: url(\'data:image/svg+xml;base64,'.Util::generateRadioButton($elementColor).'\');' .
+				'background-image: url(\'data:image/svg+xml;base64,'.$this->util->generateRadioButton($elementColor).'\');' .
 				"}\n";
 			$responseCss .= '
 				#firstrunwizard .firstrunwizard-header {
@@ -265,7 +276,7 @@ class ThemingController extends Controller {
 				'background-image: url(\'./loginbackground?v='.$cacheBusterValue.'\');' .
 			'}' . "\n";
 		}
-		if(Util::invertTextColor($color)) {
+		if($this->util->invertTextColor($color)) {
 			$responseCss .= '#header .header-appname, #expandDisplayName { color: #000000; }' . "\n";
 			$responseCss .= '#header .icon-caret { background-image: url(\'' . \OC::$WEBROOT . '/core/img/actions/caret-dark.svg\'); }' . "\n";
 			$responseCss .= '.searchbox input[type="search"] { background: transparent url(\'' . \OC::$WEBROOT . '/core/img/actions/search.svg\') no-repeat 6px center; color: #000; }' . "\n";
@@ -273,7 +284,7 @@ class ThemingController extends Controller {
 		}
 
 		$response = new DataDownloadResponse($responseCss, 'style', 'text/css');
-		$response->addHeader('Expires', date(\DateTime::RFC2822));
+		$response->addHeader('Expires', date(\DateTime::RFC2822, $this->timeFactory->getTime()));
 		$response->cacheFor(3600);
 		return $response;
 	}
diff --git a/apps/theming/lib/Template.php b/apps/theming/lib/Template.php
index 8cd2befc1d..25730aad95 100644
--- a/apps/theming/lib/Template.php
+++ b/apps/theming/lib/Template.php
@@ -40,7 +40,7 @@ use OCP\IURLGenerator;
 class Template extends \OC_Defaults {
 	/** @var IConfig */
 	private $config;
-	/** @var  IL10N */
+	/** @var IL10N */
 	private $l;
 	/** @var IURLGenerator */
 	private $urlGenerator;
diff --git a/apps/theming/lib/Util.php b/apps/theming/lib/Util.php
index f0ce30ac5b..71ed0958e4 100644
--- a/apps/theming/lib/Util.php
+++ b/apps/theming/lib/Util.php
@@ -29,8 +29,8 @@ class Util {
 	 * @param string $color rgb color value
 	 * @return bool
 	 */
-	public static function invertTextColor($color) {
-		$l = self::calculateLuminance($color);
+	public function invertTextColor($color) {
+		$l = $this->calculateLuminance($color);
 		if($l>0.5) {
 			return true;
 		} else {
@@ -44,8 +44,8 @@ class Util {
 	 * @param $color
 	 * @return string
 	 */
-	public static function elementColor($color) {
-		$l = self::calculateLuminance($color);
+	public function elementColor($color) {
+		$l = $this->calculateLuminance($color);
 		if($l>0.8) {
 			return '#555555';
 		} else {
@@ -57,7 +57,7 @@ class Util {
 	 * @param string $color rgb color value
 	 * @return float
 	 */
-	public static function calculateLuminance($color) {
+	public function calculateLuminance($color) {
 		$hex = preg_replace("/[^0-9A-Fa-f]/", '', $color);
 		if (strlen($hex) === 3) {
 			$hex = $hex{0} . $hex{0} . $hex{1} . $hex{1} . $hex{2} . $hex{2};
@@ -75,7 +75,7 @@ class Util {
 	 * @param $color
 	 * @return string base64 encoded radio button svg
 	 */
-	public static function generateRadioButton($color) {
+	public function generateRadioButton($color) {
 		$radioButtonIcon = '<svg xmlns="http://www.w3.org/2000/svg" height="16" width="16">' .
 			'<path d="M8 1a7 7 0 0 0-7 7 7 7 0 0 0 7 7 7 7 0 0 0 7-7 7 7 0 0 0-7-7zm0 1a6 6 0 0 1 6 6 6 6 0 0 1-6 6 6 6 0 0 1-6-6 6 6 0 0 1 6-6zm0 2a4 4 0 1 0 0 8 4 4 0 0 0 0-8z" fill="'.$color.'"/></svg>';
 		return base64_encode($radioButtonIcon);
diff --git a/apps/theming/tests/Controller/ThemingControllerTest.php b/apps/theming/tests/Controller/ThemingControllerTest.php
index c9b55001f8..c5a947cc8b 100644
--- a/apps/theming/tests/Controller/ThemingControllerTest.php
+++ b/apps/theming/tests/Controller/ThemingControllerTest.php
@@ -42,6 +42,10 @@ class ThemingControllerTest extends TestCase {
 	private $config;
 	/** @var Template */
 	private $template;
+	/** @var Util */
+	private $util;
+	/** @var \OCP\AppFramework\Utility\ITimeFactory */
+	private $timeFactory;
 	/** @var IL10N */
 	private $l10n;
 	/** @var ThemingController */
@@ -54,14 +58,24 @@ class ThemingControllerTest extends TestCase {
 		$this->config = $this->getMock('\\OCP\\IConfig');
 		$this->template = $this->getMockBuilder('\\OCA\\Theming\\Template')
 			->disableOriginalConstructor()->getMock();
+		$this->util = new Util();
+		$this->timeFactory = $this->getMockBuilder('OCP\AppFramework\Utility\ITimeFactory')
+			->disableOriginalConstructor()
+			->getMock();
 		$this->l10n = $this->getMock('\\OCP\\IL10N');
 		$this->rootFolder = $this->getMock('\\OCP\\Files\\IRootFolder');
 
+		$this->timeFactory->expects($this->any())
+			->method('getTime')
+			->willReturn(123);
+
 		$this->themingController = new ThemingController(
 			'theming',
 			$this->request,
 			$this->config,
 			$this->template,
+			$this->util,
+			$this->timeFactory,
 			$this->l10n,
 			$this->rootFolder
 		);
@@ -273,6 +287,7 @@ class ThemingControllerTest extends TestCase {
 
 		@$expected = new Http\StreamResponse($tmpLogo);
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		$expected->addHeader('Content-Disposition', 'attachment');
 		$expected->addHeader('Content-Type', 'text/svg');
 		@$this->assertEquals($expected, $this->themingController->getLogo());
@@ -301,6 +316,7 @@ class ThemingControllerTest extends TestCase {
 
 		@$expected = new Http\StreamResponse($tmpLogo);
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		$expected->addHeader('Content-Disposition', 'attachment');
 		$expected->addHeader('Content-Type', 'image/png');
 		@$this->assertEquals($expected, $this->themingController->getLoginBackground());
@@ -344,7 +360,7 @@ class ThemingControllerTest extends TestCase {
 			$color
 		);
 		$expectedData .= 'input[type="radio"].radio:checked:not(.radio--white):not(:disabled) + label:before {' .
-			'background-image: url(\'data:image/svg+xml;base64,'.Util::generateRadioButton($color).'\');' .
+			'background-image: url(\'data:image/svg+xml;base64,'.$this->util->generateRadioButton($color).'\');' .
 			"}\n";
 
 		$expectedData .= '
@@ -359,6 +375,7 @@ class ThemingControllerTest extends TestCase {
 		$expected = new Http\DataDownloadResponse($expectedData, 'style', 'text/css');
 
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		@$this->assertEquals($expected, $this->themingController->getStylesheet());
 	}
 
@@ -399,7 +416,7 @@ class ThemingControllerTest extends TestCase {
 			\OC::$WEBROOT
 		);
 		$expectedData .= 'input[type="radio"].radio:checked:not(.radio--white):not(:disabled) + label:before {' .
-			'background-image: url(\'data:image/svg+xml;base64,'.Util::generateRadioButton('#555555').'\');' .
+			'background-image: url(\'data:image/svg+xml;base64,'.$this->util->generateRadioButton('#555555').'\');' .
 			"}\n";
 
 		$expectedData .= '
@@ -419,6 +436,7 @@ class ThemingControllerTest extends TestCase {
 		$expected = new Http\DataDownloadResponse($expectedData, 'style', 'text/css');
 
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		@$this->assertEquals($expected, $this->themingController->getStylesheet());
 	}
 
@@ -460,6 +478,7 @@ class ThemingControllerTest extends TestCase {
 		$expected = new Http\DataDownloadResponse($expectedData, 'style', 'text/css');
 
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		@$this->assertEquals($expected, $this->themingController->getStylesheet());
 	}
 
@@ -493,6 +512,7 @@ class ThemingControllerTest extends TestCase {
 		$expected = new Http\DataDownloadResponse($expectedData, 'style', 'text/css');
 
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		@$this->assertEquals($expected, $this->themingController->getStylesheet());
 	}
 
@@ -534,7 +554,7 @@ class ThemingControllerTest extends TestCase {
 			$color
 		);
 		$expectedData .= 'input[type="radio"].radio:checked:not(.radio--white):not(:disabled) + label:before {' .
-			'background-image: url(\'data:image/svg+xml;base64,'.Util::generateRadioButton($color).'\');' .
+			'background-image: url(\'data:image/svg+xml;base64,'.$this->util->generateRadioButton($color).'\');' .
 			"}\n";
 		$expectedData .= '
 				#firstrunwizard .firstrunwizard-header {
@@ -565,6 +585,7 @@ class ThemingControllerTest extends TestCase {
 		$expected = new Http\DataDownloadResponse($expectedData, 'style', 'text/css');
 
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		@$this->assertEquals($expected, $this->themingController->getStylesheet());
 	}
 
@@ -606,7 +627,7 @@ class ThemingControllerTest extends TestCase {
 			\OC::$WEBROOT
 		);
 		$expectedData .= 'input[type="radio"].radio:checked:not(.radio--white):not(:disabled) + label:before {' .
-			'background-image: url(\'data:image/svg+xml;base64,'.Util::generateRadioButton('#555555').'\');' .
+			'background-image: url(\'data:image/svg+xml;base64,'.$this->util->generateRadioButton('#555555').'\');' .
 			"}\n";
 		$expectedData .= '
 				#firstrunwizard .firstrunwizard-header {
@@ -641,6 +662,7 @@ class ThemingControllerTest extends TestCase {
 		$expected = new Http\DataDownloadResponse($expectedData, 'style', 'text/css');
 
 		$expected->cacheFor(3600);
+		$expected->addHeader('Expires', date(\DateTime::RFC2822, 123));
 		@$this->assertEquals($expected, $this->themingController->getStylesheet());
 	}
 
diff --git a/apps/theming/tests/UtilTest.php b/apps/theming/tests/UtilTest.php
index cf64b389d1..c7fc385d25 100644
--- a/apps/theming/tests/UtilTest.php
+++ b/apps/theming/tests/UtilTest.php
@@ -27,62 +27,70 @@ use Test\TestCase;
 
 class UtilTest extends TestCase {
 
+	/** @var Util */
+	protected $util;
+
+	protected function setUp() {
+		parent::setUp();
+		$this->util = new Util();
+	}
+
 	public function testInvertTextColorLight() {
-		$invert = Util::invertTextColor('#ffffff');
+		$invert = $this->util->invertTextColor('#ffffff');
 		$this->assertEquals(true, $invert);
 	}
 
 	public function testInvertTextColorDark() {
-		$invert = Util::invertTextColor('#000000');
+		$invert = $this->util->invertTextColor('#000000');
 		$this->assertEquals(false, $invert);
 	}
 
 	public function testCalculateLuminanceLight() {
-		$luminance = Util::calculateLuminance('#ffffff');
+		$luminance = $this->util->calculateLuminance('#ffffff');
 		$this->assertEquals(1, $luminance);
 	}
 
 	public function testCalculateLuminanceDark() {
-		$luminance = Util::calculateLuminance('#000000');
+		$luminance = $this->util->calculateLuminance('#000000');
 		$this->assertEquals(0, $luminance);
 	}
 
 	public function testCalculateLuminanceLightShorthand() {
-		$luminance = Util::calculateLuminance('#fff');
+		$luminance = $this->util->calculateLuminance('#fff');
 		$this->assertEquals(1, $luminance);
 	}
 
 	public function testCalculateLuminanceDarkShorthand() {
-		$luminance = Util::calculateLuminance('#000');
+		$luminance = $this->util->calculateLuminance('#000');
 		$this->assertEquals(0, $luminance);
 	}
 	public function testInvertTextColorInvalid() {
-		$invert = Util::invertTextColor('aaabbbcccddd123');
+		$invert = $this->util->invertTextColor('aaabbbcccddd123');
 		$this->assertEquals(false, $invert);
 	}
 	
 	public function testInvertTextColorEmpty() {
-		$invert = Util::invertTextColor('');
+		$invert = $this->util->invertTextColor('');
 		$this->assertEquals(false, $invert);
 	}
 
 	public function testElementColorDefault() {
-		$elementColor = Util::elementColor("#000000");
+		$elementColor = $this->util->elementColor("#000000");
 		$this->assertEquals('#000000', $elementColor);
 	}
 
 	public function testElementColorOnBrightBackground() {
-		$elementColor = Util::elementColor('#ffffff');
+		$elementColor = $this->util->elementColor('#ffffff');
 		$this->assertEquals('#555555', $elementColor);
 	}
 
 	public function testGenerateRadioButtonWhite() {
-		$button = Util::generateRadioButton('#ffffff');
+		$button = $this->util->generateRadioButton('#ffffff');
 		$expected = 'PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIGhlaWdodD0iMTYiIHdpZHRoPSIxNiI+PHBhdGggZD0iTTggMWE3IDcgMCAwIDAtNyA3IDcgNyAwIDAgMCA3IDcgNyA3IDAgMCAwIDctNyA3IDcgMCAwIDAtNy03em0wIDFhNiA2IDAgMCAxIDYgNiA2IDYgMCAwIDEtNiA2IDYgNiAwIDAgMS02LTYgNiA2IDAgMCAxIDYtNnptMCAyYTQgNCAwIDEgMCAwIDggNCA0IDAgMCAwIDAtOHoiIGZpbGw9IiNmZmZmZmYiLz48L3N2Zz4=';
 		$this->assertEquals($expected, $button);
 	}
 	public function testGenerateRadioButtonBlack() {
-		$button = Util::generateRadioButton('#000000');
+		$button = $this->util->generateRadioButton('#000000');
 		$expected = 'PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIGhlaWdodD0iMTYiIHdpZHRoPSIxNiI+PHBhdGggZD0iTTggMWE3IDcgMCAwIDAtNyA3IDcgNyAwIDAgMCA3IDcgNyA3IDAgMCAwIDctNyA3IDcgMCAwIDAtNy03em0wIDFhNiA2IDAgMCAxIDYgNiA2IDYgMCAwIDEtNiA2IDYgNiAwIDAgMS02LTYgNiA2IDAgMCAxIDYtNnptMCAyYTQgNCAwIDEgMCAwIDggNCA0IDAgMCAwIDAtOHoiIGZpbGw9IiMwMDAwMDAiLz48L3N2Zz4=';
 		$this->assertEquals($expected, $button);
 	}