Removing dates is typically done to prevent viewers from becoming aware of a decrease in posts. Is that why they've been removed?
I'm not sure if I know what you mean. Dates should not have been removed, there's still shown on each post in the top right.
@Peanits it appears that the smaller screen adaptations of the site, remove the date/time from the list pages (i.e. Forum list, Thread list, etc.), and the smallest screen size completely removes it from the messages themselves.