current_time( 'mysql' ) returns local site time: 2021-03-04 17:43:15
current_time( 'mysql', 1 ) returns GMT: 2021-03-04 06:43:15
current_time( 'timestamp' ) returns local site time: 2021-03-05 04:43:15
current_time( 'timestamp', 1 ) returns GMT: 2021-03-04 17:43:15