I think it is ok, all I can suggest you is:
-Go to advanced editor(at options(wheel))
- Select "cell_details"
-Delete "cell_details"(Remove button(at up-right)
-Cilck on "save changes"(left-down)
After this action, if you go again to your gallery, the problem should be fixed.
Now, if you want to show the long date, do what greg said:
-"see how NAML generates this page" > options(wheel) > search macro
-Search "cell_details"
-"edit this override"
-Itroduce this at line 6:
<div class="weak-color" style="width:100%;font-size:80%;margin:.3em 0;font-variant: small-caps;">
<n.page_node.when_created.long_format/>
</div>
-Click on "save changes"
Now, your problem should be fixed
:) Helper