"So i want to do partitions based on date column"
Why ? You need a *justification*, a reason that you would act on. Just because a table is big does not automatically mean it should be partitioned. The way you intend to *use* the table has a much larger bearing.
"I want to use hash partitioning on date column"
Why ?
"Also please tell me what key should i user global or local?"
It depends. If local was *always* better, we would phase out global indexes, and vice versa.
Not trying to be curt, but I'd strongly advise having a reasonable good read on the concepts and then use that knowledge to make a practical decision
http://docs.oracle.com/database/121/VLDBG/GUID-EA7EF5CB-DD49-43AF-889A-F83AAC0D7D51.htm#VLDBG002