毫秒转换为日期 

SELECT TO_CHAR(1406538765000 / (1000 * 60 * 60 * 24) +      
        TO_DATE('1970-01-01 08:00:00', 'YYYY-MM-DD HH:MI:SS'), 'YYYY-MM-DD HH24:MI:SS') AS CDATE      
 FROM DUAL; 

日期转换毫秒

 SELECT TO_NUMBER(TO_DATE('2014-07-28 17:12:45', 'YYYY-MM-DD HH24:MI:SS') -      
                 TO_DATE('1970-01-01 8:0:0', 'YYYY-MM-DD HH24:MI:SS')) * 24 * 60 * 60 * 1000      
  FROM DUAL; 

获取系统当前时间

select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;