diff --git a/includes/api/ApiBlockInfoTrait.php b/includes/api/ApiBlockInfoTrait.php
index e0f8bddb9ce..7c94670a0a7 100644
--- a/includes/api/ApiBlockInfoTrait.php
+++ b/includes/api/ApiBlockInfoTrait.php
@@ -36,7 +36,10 @@ trait ApiBlockInfoTrait {
 	 *  - blockedbyid - user ID of the blocker
 	 *  - blockreason - reason provided for the block
 	 *  - blockedtimestamp - timestamp for when the block was placed/modified
+	 *  - blockedtimestampformatted - blockedtimestamp, formatted for the current locale
 	 *  - blockexpiry - expiry time of the block
+	 *  - blockexpiryformatted - blockexpiry formatted for the current locale, omitted if infinite
+	 *  - blockexpiryrelative - relative time to blockexpiry (e.g. 'in 5 days'), omitted if infinite
 	 *  - blockpartial - block only applies to certain pages, namespaces and/or actions
 	 *  - systemblocktype - system block type, if any
 	 */
@@ -57,11 +60,26 @@ trait ApiBlockInfoTrait {
 		$vals['blockreason'] = $block->getReasonComment()
 			->message->inLanguage( $language )->plain();
 		$vals['blockedtimestamp'] = wfTimestamp( TS_ISO_8601, $block->getTimestamp() );
-		$vals['blockexpiry'] = ApiResult::formatExpiry( $block->getExpiry(), 'infinite' );
+		$expiry = ApiResult::formatExpiry( $block->getExpiry(), 'infinite' );
+		$vals['blockexpiry'] = $expiry;
 		$vals['blockpartial'] = !$block->isSitewide();
 		$vals['blocknocreate'] = $block->isCreateAccountBlocked();
 		$vals['blockanononly'] = !$block->isHardblock();
 
+		$user = $this->getUser();
+		// Formatted timestamps
+		$vals['blockedtimestampformatted'] = $language->formatExpiry(
+			$block->getTimestamp(), true, 'infinity', $user
+		);
+		if ( $expiry !== 'infinite' ) {
+			$vals['blockexpiryformatted'] = $language->formatExpiry(
+				$expiry, true, 'infinity', $user
+			);
+			$vals['blockexpiryrelative'] = $language->getHumanTimestamp(
+				new MWTimestamp( $expiry ), new MWTimestamp(), $user
+			);
+		}
+
 		if ( $block instanceof SystemBlock ) {
 			$vals['systemblocktype'] = $block->getSystemBlockType();
 		}
@@ -80,6 +98,12 @@ trait ApiBlockInfoTrait {
 	 */
 	abstract public function getLanguage();
 
+	/**
+	 * @see IContextSource::getUser
+	 * @return User
+	 */
+	abstract public function getUser();
+
 	/** @} */
 	// endregion -- end of methods required from ApiBase
 
diff --git a/tests/phpunit/includes/api/ApiBaseTest.php b/tests/phpunit/includes/api/ApiBaseTest.php
index 4409cf83c1e..223bb42166a 100644
--- a/tests/phpunit/includes/api/ApiBaseTest.php
+++ b/tests/phpunit/includes/api/ApiBaseTest.php
@@ -1347,7 +1347,8 @@ class ApiBaseTest extends ApiTestCase {
 		MediaWikiServices::getInstance()->getDatabaseBlockStore()->insertBlock( $block );
 
 		$mockTrait = $this->getMockForTrait( ApiBlockInfoTrait::class );
-		$mockTrait->method( 'getLanguage' )->willReturn( 'en' );
+		$language = MediaWikiServices::getInstance()->getLanguageFactory()->getLanguage( 'en' );
+		$mockTrait->method( 'getLanguage' )->willReturn( $language );
 		$userInfoTrait = TestingAccessWrapper::newFromObject( $mockTrait );
 		$blockinfo = [ 'blockinfo' => $userInfoTrait->getBlockDetails( $block ) ];
 
@@ -1406,7 +1407,8 @@ class ApiBaseTest extends ApiTestCase {
 		MediaWikiServices::getInstance()->getDatabaseBlockStore()->insertBlock( $block );
 
 		$mockTrait = $this->getMockForTrait( ApiBlockInfoTrait::class );
-		$mockTrait->method( 'getLanguage' )->willReturn( 'en' );
+		$language = MediaWikiServices::getInstance()->getLanguageFactory()->getLanguage( 'en' );
+		$mockTrait->method( 'getLanguage' )->willReturn( $language );
 		$userInfoTrait = TestingAccessWrapper::newFromObject( $mockTrait );
 		$blockinfo = [ 'blockinfo' => $userInfoTrait->getBlockDetails( $block ) ];
 
diff --git a/tests/phpunit/includes/api/ApiBlockInfoTraitTest.php b/tests/phpunit/includes/api/ApiBlockInfoTraitTest.php
index 65eece7e9d2..70c4e9a196a 100644
--- a/tests/phpunit/includes/api/ApiBlockInfoTraitTest.php
+++ b/tests/phpunit/includes/api/ApiBlockInfoTraitTest.php
@@ -2,6 +2,7 @@
 
 use MediaWiki\Block\DatabaseBlock;
 use MediaWiki\Block\SystemBlock;
+use MediaWiki\MediaWikiServices;
 use Wikimedia\TestingAccessWrapper;
 
 /**
@@ -12,8 +13,9 @@ class ApiBlockInfoTraitTest extends MediaWikiIntegrationTestCase {
 	 * @dataProvider provideGetBlockDetails
 	 */
 	public function testGetBlockDetails( $block, $expectedInfo ) {
+		$language = MediaWikiServices::getInstance()->getLanguageFactory()->getLanguage( 'en' );
 		$mock = $this->getMockForTrait( ApiBlockInfoTrait::class );
-		$mock->method( 'getLanguage' )->willReturn( 'en' );
+		$mock->method( 'getLanguage' )->willReturn( $language );
 		$info = TestingAccessWrapper::newFromObject( $mock )->getBlockDetails( $block );
 		$subset = array_merge( [
 			'blockid' => null,