public static function sort_core_themes( $theme_a, $theme_b ) {

		static $twenties = array(
			'Twenty Ten',
			'Twenty Eleven',
			'Twenty Twelve',
			'Twenty Thirteen',
			'Twenty Fourteen',
			'Twenty Fifteen',
			'Twenty Sixteen',
			'Twenty Seventeen',
			'Twenty Eighteen',
			'Twenty Nineteen',
			'Twenty Twenty',
		);

		if ( 0 === strpos( $theme_a, 'Twenty' ) && 0 === strpos( $theme_b, 'Twenty' ) ) {

			$index_a = array_search( $theme_a, $twenties, true );
			$index_b = array_search( $theme_b, $twenties, true );

			if ( false !== $index_a && false !== $index_b ) {
				return ( $index_a < $index_b ) ? - 1 : 1;
			}
		}

		return strcasecmp( $theme_a, $theme_b );
	}