Another holiday, another apostrophe-based conundrum. The day on which we celebrate our mothers is almost upon us here in the UK, so what should we write on our card? Indeed, which card should we buy? Is it the day that belongs to all the mothers or just our individual mother? Or is it a day for mothers but not belonging to them at all?
The OED goes with Mother’s Day which I think works. A lot of us have only one mum and it’s her day. Celebration in the singular. General usage seems to back this up.
It seems Ann and Anna Jarvis, the women who invented Mother’s Day in the USA, chose to have the apostrophe before the S too, ‘[Anna] was specific about the location of the apostrophe; it was to be a singular possessive, for each family to honour their mother, not a plural possessive commemorating all mothers in the world.’
She also thought that we should send letters, rather than cards.
I think that’s pretty conclusive, but if you’re still not happy, just go with Mothering Sunday.