postgresql version of mysql UNIX_TIMESTAMP()

MySQL

mysql> SELECT UNIX_TIMESTAMP();
mysql> SELECT UNIX_TIMESTAMP('1973-11-29 21:33:09');

PostgreSQL

postgres=> SELECT EXTRACT(EPOCH FROM CURRENT_TIMESTAMP(0));
postgres=> SELECT EXTRACT(EPOCH FROM TIMESTAMP '1973-11-29 21:33:09');

MySQL from_unixtime and unix_timestamp