Index: src/wp-includes/date.php
===================================================================
--- src/wp-includes/date.php	(revision 30993)
+++ src/wp-includes/date.php	(working copy)
@@ -336,17 +336,7 @@
 		);
 
 		// Weeks per year.
-		if ( array_key_exists( 'year', $date_query ) ) {
-			// If we have a specific year, use it to calculate number of weeks.
-			$date = new DateTime();
-			$date->setISODate( $date_query['year'], 53 );
-			$week_count = $date->format( "W" ) === "53" ? 53 : 52;
-
-		} else {
-			// Otherwise set the week-count to a maximum of 53.
-			$week_count = 53;
-		}
-
+		$week_count = (array_key_exists('year', $date_query) ? date('W',mktime(0,0,0,12,28,$date_query['year'])) : 53);
 		$min_max_checks['week'] = array(
 			'min' => 1,
 			'max' => $week_count