It has been possible to make batch changes to CiviCRM data using VBO (Views Bulk Operations) for a while but I only just got around to implementing it for a customer so I am taking the chance to document what I did here!
The recipe is basically
- install civicrm_entity version 2.x & vbo
- create a View
- add and configure the desired 'bulk operation'
And, setting up a View with a bulk operation to modify Relationship End Dates was pretty much that easy
Install CiviCRM Entity version 2.x