current_time( 'mysql' ) returns local site time: 2021-08-02 14:45:46
current_time( 'mysql', 1 ) returns GMT: 2021-08-02 04:45:46
current_time( 'timestamp' ) returns local site time: 2021-08-02 14:45:46
current_time( 'timestamp', 1 ) returns GMT: 2021-08-02 04:45:46