数据库自定义函数，date和utc时间相互转换的代码实例

  /**
  * 根据日期获得utc值
  */
create or replace function fun_date2utc(p_date in date) return number is  utc number;
begin
   utc := 86400 * (p_date - to_date('1970/01/01 00:00:00', 'YYYY/MM/DD HH24:MI:SS')) - 8*3600;
   return utc;
end fun_date2utc;


  /*-- name: utc2date
  -- return: date
  -- param: p_utc [in] NUMBER: UTC(s)根据utc转成日期
  */
create or replace function fun_utc2date(p_utc in NUMBER) return DATE is  p_date DATE;
begin
   p_date := (p_utc + 8*3600) / 86400 + to_date('1970/01/01 00:00:00', 'YYYY/MM/DD HH24:MI:SS');
   return p_date;
end fun_utc2date;