CREATE OR REPLACE FUNCTION Unix_To_Oracle_Date
(
   p_unix_date IN NUMBER,  -- Range of >= 0
   p_num_hr_gmt_diff IN PLS_INTEGER    -- Range of -24 to +24

) RETURN DATE AS

/*
   Function Name:    Unix_To_Oracle_Date

   Purpose:          To calculate an Oracle date based on a Unix GMT date
                     in seconds, since the epoch of Unix (January 1st, 1970).

                     The date returned will be based on the number of hours
                     the oracle database system clock is either ahead or behind
                     the Greenwich Mean Time line.

                     If the parameters do not fall within the specified ranges
                     then the returned date will be NULL.

   Developer Name:   Giovanni Jaramillo
   Developer Email:  Giovanni@CheckOut.com
   Creation Date:    Copyright ? CheckOut.com December 2, 1999

   Parameters:       p_unix_date of NUMBER type (Range is > 0 only)
                     p_num_hr_gmt_diff of PLS_INTEGER type (Range -24 to +24)

   Input:            NONE
   Output:           NONE
   Returned value:   DATE := Unix_To_Oracle_Date(p_Unix_Date);

*/

   -- CONSTANTS

   -- These 2 CONSTANTS below are of POSITIVE type to indicate that they
   -- CANNOT be less than 1

   c_SECONDS_IN_DAY CONSTANT POSITIVE := 86400;
   c_HOURS_IN_DAY CONSTANT POSITIVE := 24;

   c_UNIX_EPOCH_DATE_TIME_STRING CONSTANT VARCHAR2(50) := '01/01/1970 00:00:00';
   c_DATE_FORMAT CONSTANT VARCHAR2(50) := 'MM/DD/YYYY HH24:MI:SS';

   -- VARIABLES

   v_sql_code PLS_INTEGER;
   v_sql_error_message VARCHAR2(512);

   -- The 2 variables have to be of NUMBER type because a PLS_INTEGER divided by
   -- another PLS_INTEGER can result in a fraction, thus the result must be of
   -- NUMBER type only

   v_unix_seconds NUMBER;
   v_gmt_time_gap NUMBER;

   v_return_value DATE;

BEGIN

   IF(NOT (p_num_hr_gmt_diff < (-c_HOURS_IN_DAY)) AND
      NOT (p_num_hr_gmt_diff > (c_HOURS_IN_DAY))) THEN

      v_unix_seconds := (p_unix_date / c_SECONDS_IN_DAY);
      v_gmt_time_gap := (p_num_hr_gmt_diff / c_HOURS_IN_DAY);

      v_return_value := TO_DATE(c_UNIX_EPOCH_DATE_TIME_STRING, c_DATE_FORMAT) +
                        v_unix_seconds + v_gmt_time_gap;
   ELSE
      v_return_value := NULL;
   END IF;

   RETURN(v_return_value);

EXCEPTION

   WHEN OTHERS THEN
      v_sql_code := SQLCODE;
      v_sql_error_message := SQLERRM(v_sql_code);

      DBMS_OUTPUT.PUT_LINE('OTHER ERROR');
      DBMS_OUTPUT.PUT_LINE(v_sql_error_message);

END Unix_To_Oracle_Date;