Hmmm...not sure about "majority of European countries." Moreover, since the namedays are descended from Roman Catholic calendar of saints, I'm pretty sure there

Hmmm...not sure about "majority of European countries." Moreover, since the namedays are descended from Roman Catholic calendar of saints, I'm pretty sure there would be uproar over Facebook having an overt religious preference (regardless of reality). Anyway, a short search has brought forth a plethora of FB apps providing just this functionality; not sure why it should be implemented in "core" FB. (And the obligatory disclaimer: even all European FB users wouldn't even be a simple majority of all FB users; building in such a feature for a fraction of users would inevitably lead to other factions crying for their own specialized metadata, leading to fragmented FB experience)