Hi iftomkins,
The documentation has been updated in that we have removed message.post_date as an accepted parameter. This means that filing a support ticket is still required to edit the post dates. Please post an idea for this to our idea exchange. I know this would be useful for many customers.
nathan It's not that the feature was removed, rather it cannot be used externally by customers. It was documented externally by mistake. It will take engineering resources to expose this properly, so making noise on the Dev Network and the idea exchange is the best way to get this on the radar for our backlong/roadmap.
