FunctionName(10.02.2011) Result should be 31.01.2011

select <date> - datepart('day', <date>) - 1

select date(current_Date) - datepart('day', current_Date) - 1

select current_timestamp, current_timestamp - extract(day from current_timestamp)

2012-10-05 13:35:05 2012-09-30 00:00:00