Dydd Gŵyl Dewi Hapus! (yn Cymraeg/in Welsh). I was gong to put both versions Welsh and English in the title but that would have been a bit long! 1st March is 'the feast day of Saint David', the patron saint of Wales. The date we celebrate St David's Day is actually the day that he died back in 589 AD. I've done a bit of research as I've not studied it since school!