Quarterly partition non-deterministic error

Hello All,

I am trying to change table's partition expression from monthly to quarterly.

The  column on which the partition is made is an integer column having value like
20120230

I tried this query to extract the quaerter for each year and see my partition_key

select distinct(partition_key) from (select cast((EXTRACT(year FROM cast(cast(xxxx as varchar)as date))*100 + extract (quarter from cast(cast(xxxx as varchar)as date))) as varchar) as partition_key from xx.xxxx) sub

Got result as was expecting

201104
201203


But now I try to implement the same while changing partition for a table this way

ALTER TABLE xx.xxxx PARTITION BY (EXTRACT(year FROM cast(cast(xxxx as varchar)as date))*100 + extract (quarter from cast(cast(xxxx as varchar)as date))) ;

I get this error

NOTICE 4954:  The new partitioning scheme will produce 3 partitionsROLLBACK 2552:  Cannot use meta function or non-deterministic function in PARTITION BY expression

What is  a non-deterministic function and any other way I can achieve quarterly partition on my data.

Thanks