views - how to filter by birthdays dependent on the current date
So it looks like a custom filter is in order. They are relatively simple to make. There are a few tutorials out there. Look up “custom views filter handler” here or elsewhere. I’ve made custom contextual filters and sort handlers several times. “Contextual range filter” and “Views Raw SQL”. You can look at the code for them on Drupal.org. I think this would be a good candidate for something worth releasing as an official module. You could call it “Anniversary Date Filter” or something.