In message 849f98ed05020914363e274be7@mail.gmail.com, Mark Williamson node.ue-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org writes
Not to spoil your fun, but unlike Christmas there is a much more international greeting for the same holiday (Valentine's Day) that is much less likely to alienate or offend others.
There is no way to say "Happy valentine's day" in O'odham (Pima/Papago) or Piipaash (Maricopa) or Xalychidoma (Halichidhoma) without sounding extremely strange and perhaps overly religious - it is definitely non-traditional and not all speakers of these languages (well, at least O'odham) know what it is.
Indeed. It's a cultural thing -- even in Europe, I'm not sure how we'd say it in Welsh as our equivalent is St Dwynwen's Day (25th January). We had plenty of our own saints and had no need to import Roman ones!