On the Open Data tab of ArcGIS Hub the dates for the listed items relate to the Publication Date stored in the metadata rather than the Feature Layer's last updated date:
Feature Layer's Metadata:
On the Items tab (when logged in) it records the Feature Layer's last updated date. I think this is preferable as I suspect most people don't update the metadata Publication Date every time their data is updated (our Feature Layers are updated weekly via a script):
Feature Layer's last Updated date:
The same inconsistency applies for the licensing, with one showing a CC-BY image (which is correct) and the other showing 'Custom License'. Any explanation for the differences Graham Hudgins?