diff --git a/src/wp-admin/themes.php b/src/wp-admin/themes.php
index 52e3531250..4e63fd82f0 100644
--- a/src/wp-admin/themes.php
+++ b/src/wp-admin/themes.php
@@ -222,7 +222,12 @@ foreach ( $themes as $theme ) :
 	<div class="theme-author"><?php printf( __( 'By %s' ), $theme['author'] ); ?></div>
 
 	<?php if ( $theme['active'] ) { ?>
-		<h3 class="theme-name" id="<?php echo $aria_name; ?>"><span><?php _ex( 'Active:', 'theme' ); ?></span> <?php echo $theme['name']; ?></h3>
+		<h3 class="theme-name" id="<?php echo $aria_name; ?>">
+			<?php
+			/* translators: %s: theme name */
+			printf( __( '<span>Active:</span> %s' ), $theme['name'] );
+			?>
+		</h3>
 	<?php } else { ?>
 		<h3 class="theme-name" id="<?php echo $aria_name; ?>"><?php echo $theme['name']; ?></h3>
 	<?php } ?>
@@ -319,7 +324,12 @@ $can_delete = current_user_can( 'delete_themes' );
 	<div class="theme-author"><?php printf( __( 'By %s' ), '{{{ data.author }}}' ); ?></div>
 
 	<# if ( data.active ) { #>
-		<h3 class="theme-name" id="{{ data.id }}-name"><span><?php _ex( 'Active:', 'theme' ); ?></span> {{{ data.name }}}</h3>
+		<h3 class="theme-name" id="{{ data.id }}-name">
+			<?php
+			/* translators: %s: theme name */
+			printf( __( '<span>Active:</span> %s' ), '{{ data.name }}' );
+			?>
+		></h3>
 	<# } else { #>
 		<h3 class="theme-name" id="{{ data.id }}-name">{{{ data.name }}}</h3>
 	<# } #>
diff --git a/src/wp-includes/class-wp-customize-control.php b/src/wp-includes/class-wp-customize-control.php
index bd964c2d6f..c220f2a921 100644
--- a/src/wp-includes/class-wp-customize-control.php
+++ b/src/wp-includes/class-wp-customize-control.php
@@ -1213,7 +1213,12 @@ class WP_Customize_Theme_Control extends WP_Customize_Control {
 			<div class="theme-author"><?php printf( __( 'By %s' ), '{{ data.theme.author }}' ); ?></div>
 
 			<# if ( data.theme.active ) { #>
-				<h3 class="theme-name" id="{{ data.theme.id }}-name"><span><?php _ex( 'Previewing:', 'theme' ); ?></span> {{ data.theme.name }}</h3>
+				<h3 class="theme-name" id="{{ data.theme.id }}-name">
+					<?php
+					/* translators: %s: theme name */
+					printf( __( '<span>Previewing:</span> %s' ), '{{ data.theme.name }}' );
+					?>
+				</h3>
 			<# } else { #>
 				<h3 class="theme-name" id="{{ data.theme.id }}-name">{{ data.theme.name }}</h3>
 			<# } #>
@@ -1286,7 +1291,7 @@ class WP_Widget_Area_Customize_Control extends WP_Customize_Control {
 
 		<span class="reorder-toggle" tabindex="0">
 			<span class="reorder"><?php _ex( 'Reorder', 'Reorder widgets in Customizer' ); ?></span>
-			<span class="reorder-done"><?php _ex( 'Done', 'Cancel reordering widgets in Customizer'  ); ?></span>
+			<span class="reorder-done"><?php _ex( 'Done', 'Cancel reordering widgets in Customizer' ); ?></span>
 		</span>
 		<?php
 	}
diff --git a/src/wp-includes/class-wp-customize-section.php b/src/wp-includes/class-wp-customize-section.php
index b824173bdb..c2afac6d1e 100644
--- a/src/wp-includes/class-wp-customize-section.php
+++ b/src/wp-includes/class-wp-customize-section.php
@@ -353,7 +353,7 @@ class WP_Customize_Themes_Section extends WP_Customize_Section {
 					<a href="<?php echo admin_url( 'theme-install.php' ); ?>" target="_top" class="add-new-h2"><?php echo esc_html_x( 'Add New', 'Add new theme' ); ?></a>
 				<?php endif; ?>
 				</h2>
-				<div class="theme-overlay" tabindex="0" role="dialog" aria-label="<?php esc_attr_e( 'Theme details' ); ?>"></div>
+				<div class="theme-overlay" tabindex="0" role="dialog" aria-label="<?php esc_attr_e( 'Theme Details' ); ?>"></div>
 				<div id="customize-container"></div>
 				<?php if ( 6 < count( $this->controls ) ) : ?>
 					<p><label for="themes-filter">
diff --git a/src/wp-includes/post-template.php b/src/wp-includes/post-template.php
index 800a93d88a..22acff563f 100644
--- a/src/wp-includes/post-template.php
+++ b/src/wp-includes/post-template.php
@@ -1700,7 +1700,7 @@ function wp_post_revision_title( $revision, $link = true ) {
 		return false;
 
 	/* translators: revision date format, see http://php.net/date */
-	$datef = _x( 'F j, Y @ H:i', 'revision date format');
+	$datef = _x( 'F j, Y @ H:i:s', 'revision date format' );
 	/* translators: 1: date */
 	$autosavef = _x( '%1$s [Autosave]', 'post revision title extra' );
 	/* translators: 1: date */
@@ -1736,7 +1736,7 @@ function wp_post_revision_title_expanded( $revision, $link = true ) {
 
 	$author = get_the_author_meta( 'display_name', $revision->post_author );
 	/* translators: revision date format, see http://php.net/date */
-	$datef = _x( 'F j, Y @ H:i:s', 'revision date format');
+	$datef = _x( 'F j, Y @ H:i:s', 'revision date format' );
 
 	$gravatar = get_avatar( $revision->post_author, 24 );
 
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index 0d2a8505aa..90ef7996ca 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -479,7 +479,9 @@ function wp_default_scripts( &$scripts ) {
 			'newPost' => __( 'Title' ),
 			'unexpectedError' => __( 'Sorry, but an unexpected error occurred.' ),
 			'saveAlert' => __( 'The changes you made will be lost if you navigate away from this page.' ),
+			/* translators: %d: nth embed found in a post */
 			'suggestedEmbedAlt' => __( 'Suggested embed #%d' ),
+			/* translators: %d: nth image found in a post */
 			'suggestedImgAlt' => __( 'Suggested image #%d' ),
 		) );
 
diff --git a/src/wp-includes/widgets.php b/src/wp-includes/widgets.php
index 7c282c52d7..5e3431ff10 100644
--- a/src/wp-includes/widgets.php
+++ b/src/wp-includes/widgets.php
@@ -804,7 +804,8 @@ function register_sidebar($args = array()) {
 	$i = count($wp_registered_sidebars) + 1;
 
 	if ( empty( $args['id'] ) ) {
-		_doing_it_wrong( __FUNCTION__, sprintf( __( 'You should set %s in the arguments array.' ), 'id' ), '4.2.0' );
+		/* translators: %s: the id argument */
+		_doing_it_wrong( __FUNCTION__, sprintf( __( 'You should set %s in the arguments array.' ), '<code>id</code>' ), '4.2.0' );
 	}
 
 	$defaults = array(