I was curious, because I'm working with the same feature. So I looked at your pages. They match, except for the order the items are listed. Seven on both pages.

I tweaked the code to output the actual DoB for each entry to help understand what is happening, and ruled out caching issues. Also resolved the sorting issue so they now appear in the order of birthdays...

and discovered that...  it was a date culture issue - reversal of day/month when the Feed Manager accesses the feed (or apparently when you access it from a US browser). So the Feed Manager was retrieving a completely different set of people from what I was seeing in the browser from the feed. The ones we/you saw on the page all have DoB like "09/03/1984" which is not within the last 30 days in the UK, but is for USA.

Of course this means the following line in my RSS handler was using the client culture, and this must be USA when mojoPortal calls the feed, but UK from my browser:    DateTime.TryParse(dr("DoB").ToString(), DoB)

Because all my users on this site are UK, I've now changed this to

Dim ukCulture As CultureInfo = New CultureInfo("en-GB")

DateTime.TryParse(dr("DoB").ToString(), ukCulture.DateTimeFormat, DateTimeStyles.AssumeLocal, DoB)

Ahhh the page is now displaying the correct data.

This does make me wonder whether there could be a date field in the Users table for DoB, rather than using a ntext custom property?