Converting Numbers to Dates

-- 
I have a column in a table that stores the number of seconds
since 1970, as a number ( datatype NUMBER )

e.g

taba

col1		Null	Type
----            ----    ----
seconds                 NUMBER(15)

select * from taba;

seconds
-------
844275235
844327462   etc.


How can I convert this to a date e.g 11-MAR-1997


Appreciate any comments.


Regards