Hello;
We are using FilterZen and PeopleZen for, among other things, an "upcoming birthdays" part as described here: http://roxority.com/sharepoint-zen/an-upcoming-birthdays-web-part-in-10-minutes.html

On our main site collection, the parts work as expected and described. We have just created a child site collection (and have licensed our parts appropriately) for users in a remote office (India). However, when we try to create an equivalent Upcoming Birthdays part in the new site collection (even using exported copies of the known working parts), we always get "There are no user profiles to show in this view."

Clearing the date filter allows us to see all of the people profiles in People Zen, as expected. But when we try to add the Filter Zen Date Filter for the value SPS-Birthday (filtering on rgeater than or equal to today) and connect the FilterZen and PeopleZen parts, we always get no results.

The child site collection does have different regional settings than our main site collection (our main site collection is set to English-US, the child site is set to English-Great Britain). I see that there is a field in the date filter configuration that allows you to specify the locale; we have done so as documented but with no results.

So, to sum up: We are using PeopleZen/FilterZen to filter user profiles on the value in SPS-Birthday, everything works as expected.
When we try to replicate the functionality on a child collection, using the exact same configuration, we get no results returned. The child collection is set to a different locale than our primary site collection (en-gb instead of en-us), but is otherwise the same.

Follow up: We tried changing the regional settings on the child site collection to match that of the main site collection. No change in the behavior of the date filter (no results returned).