diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index 04d624af2f..031595360e 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -3816,9 +3816,10 @@ function wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $post_p
 		$check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type = %s AND ID != %d LIMIT 1";
 		$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $slug, $post_type, $post_ID ) );
 
-		// Prevent post slugs that could result in URLs that conflict with date archives.
+		// Prevent new post slugs that could result in URLs that conflict with date archives.
+		$post = get_post( $post_ID );
 		$conflicts_with_date_archive = false;
-		if ( 'post' === $post_type && preg_match( '/^[0-9]+$/', $slug ) && $slug_num = intval( $slug ) ) {
+		if ( 'post' === $post_type && ( ! $post || $post->post_name !== $slug ) && preg_match( '/^[0-9]+$/', $slug ) && $slug_num = intval( $slug ) ) {
 			$permastructs   = array_values( array_filter( explode( '/', get_option( 'permalink_structure' ) ) ) );
 			$postname_index = array_search( '%postname%', $permastructs );
 
diff --git a/tests/phpunit/tests/post/wpUniquePostSlug.php b/tests/phpunit/tests/post/wpUniquePostSlug.php
index 325617299e..a7c306065b 100644
--- a/tests/phpunit/tests/post/wpUniquePostSlug.php
+++ b/tests/phpunit/tests/post/wpUniquePostSlug.php
@@ -186,6 +186,28 @@ class Tests_Post_WpUniquePostSlug extends WP_UnitTestCase {
 		flush_rewrite_rules();
 	}
 
+	/**
+	 * @ticket 5305
+	 */
+	public function test_slugs_resulting_in_permalinks_that_resemble_year_archives_should_not_be_suffixed_for_already_published_posts() {
+		global $wp_rewrite;
+		$wp_rewrite->init();
+		$wp_rewrite->set_permalink_structure( '/%postname%/' );
+		$wp_rewrite->flush_rules();
+
+		$p = $this->factory->post->create( array(
+			'post_type' => 'post',
+			'post_name' => 'foo',
+			'post_status' => 'publish',
+		) );
+
+		$found = wp_unique_post_slug( '2015', $p, 'publish', 'post', 0 );
+		$this->assertEquals( '2015-2', $found );
+
+		$wp_rewrite->set_permalink_structure( '' );
+		flush_rewrite_rules();
+	}
+
 	/**
 	 * @ticket 5305
 	 */