Although my own Mum died almost twenty years ago I always feel a bit sad that I no longer have a Mum. My DD will undoubtedly send a card and probably some flowers too, she really shouldn't pay the inflated prices for flowers over the Mothers Day weekend as she's watching the pennies but it's such a lovely gesture. DS is abroad so, as others have pointed out, the day varies from country to country.
It was Mothering Sunday when I was little, a home made card and a bunch of wilted primroses. Back even further, wasn't it the day that domestic staff were allowed a rare day off to visit their mothers?