Please check the last "Created on" date before responding to a post, to be sure that you're not updating something that is actually quite old.
The dates were correct on the site upgrade, but then there was a flattening of the Categories that we use, and this is when the dates were impacted. It doesn't impact all posts - but does for a large number, particularly in the CA Service Management space.
I'm not sure if this can be changed. We're looking into it. It will work itself out over time, as new content is created.
In the meantime, please be careful about responding to posts and check the last "Created on" date.