There is no supported method to purge Events manually.
However, Unified Manager (rebranded as Active IQ Unified Manager from OnCommand Unified Manager with the 9.6 release) has inroduced a feature to allow you to set Event Retention and Performance Data Retention in the UM 9.6 release. You may view the Help for this feature here: https://library.netapp.com/ecmdocs/ECMLP2853092/html/frameset.html.
Screenshot for the feature view with defaults:
Screenshot for the feature view with warning when Performance Data Retention interval is less than Event Retention interval:
sorry for insisting but is there an unsupported way to purge all data manually? let's say I want to keep data for less than 1 month that the builtin data retention offers, I want to keep them for 2 weeks only. how do I do that?