Try this, this works for SQL Server
-- Central Zone = 5 Hrs * 60 = 300
-- Eastern Zone = 4 Hrs * 60 = 240
select JSSCHJBNM, JSSCHLNCSTAT, JSSCHSTTIME, dateadd(mi,((JSSCHSTTIME-300)),'1970-01-01 00:00') "DateStartTime" FROM SY900.F91320
where JSSCHJBNM = 'XXXXXXX';