Ciao,
You can try to set the ibase_timefmt format whit (as example for date in italian style ):
ibase_timefmt( "%H:%M", IBASE_TIME );
ibase_timefmt( "%d/%m/%Y %H:%M", IBASE_TIMESTAMP );
ibase_timefmt( "%d/%m/%Y", BASE_DATE );
immediatly after the ibase_connect().
Hope that helps, ciao.