Depending on the amount of data per partition - you may also want to consider partitioning by week, month or quarter.
The partitioning decision is often tied to the tiering model of data storage. For a Bronze ingest layer, the optimal partitioning is to partition by some time value so that all data for a particular ingest is in the same partition.
For serving data - such as provided by the Gold tier, the optimal partitioning strategy is to partition so that queries require retrieval of data from the fewest partitions.
Depending on your consumption patterns, this may be best achieved by partitioning by time, region or some other business criteria.