"Mothers Day" is celebrated in America and is on May 14th.
The day on 19th March is "Mothering Sunday" but all the card makers and manufacturers of tat like mugs saying "world's best mum" want to use the same templates for both, as that saves them money, so it's insanely difficult to buy a "Mothering Sunday" card now (I buy a blank-inside-for-your-own-message one).
Everyone has a mother, and a vast number of people have a crap, absent, controlling or unpleasant one, or a lovely and much-missed one who has died, or one with whom they had a tense and unresolved unhappy relationship with but who is now dead, or one who has lost their marbles and doesn't recognise them any more.
For me, the day is primarily a day to reflect on the extent to which we all sometimes need/have needed better or different "mothering" than we have, and those of us who are mothers often feel both totally inadequate and totally unappreciated despite those being in direct opposition to one another. It's a day when there's often a lot of subtle misogyny in the air about the extent to which a woman is expected to prioritise motherhood over every other aspect of human endeavour. It's not a great day. But I have no objection to being given chocolate/flowers/a big bottle of gin, if anyone feels moved to give me such items. I don't want the mug though, thanks.