The whole mother's day thing addles my feeble brain--it's one date in France, another in the UK and yet another in the States. While my mother was alive, Mother's Day always seemed more about her, so although my kids celebrated it for me, it always felt like mum's day--my mum.
Then I came to France and it got all mixed up. I say celebrate mothers on any day that feels appropriate, maybe even 365 days a year. They're not perfect (speaking for myself) but they do the best they can (speaking for myself again.) Happy mum/mama/mère wherever you are.