convert date from numeric value to date valid format

convert date from numeric value to date valid format

I need to filter all dates which greater than, say 01 january 2011.
select * from table_name where date > '01/01/2011';
the problem is that date field store int values, here is an example:
1339011098
1336717439
1339010538
How to convert the date field on the sql query (from the int format to
date format), I need to convert it to a valid date so that I can compare
it towards the above date.
Thanx.