Partitioned indices - LOCAL or GLOBAL

Hi

We have a question on partitioned indexes

Assuming that we have a non partitioned table and we are converting that into a partitioned table. During the process, obviously the indices would have
to be partitioned as well.

Assuming that the table was partitioned on a DATE column using RANGE partitioning and there was an index on the table on DATE column prior to partitioning, can someone please explain preferrably with an illustration or example, if, after the partitioning the index should be created as LOCAL or GLOBAL? What is the criteria / guide lines for selecting whether to create the index as LOCAL or GLOBAL