Partitioning

Can someone explain how partitioning works from a management point of view.  For example .. I have a table partitioned by date, 12 partitions, 1 partition per month.  I setup historical data so my partitions are 4/09, 5/09 ... 3/10.  When 4/10 comes along,  I need to drop partition 4/09 and add 4/10 and the similar for 5/10 and so on. Does oracle handle this automatically or does this need to be managed with a job ?

Thanks

Jeff