The correct name for Mother’s Day in the UK is Mothering Sunday. Mothering Sunday is always the fourth Sunday of Lent however as the dates vary as to when Easter and Lent fall the actual Sunday chosen to celebrate it may vary. This year it falls on April 3rd
In Victorian times, it was a day when children, mainly daughters, who had gone to work as domestic servants were given a day off to visit their mother and family. Today it is a day when children give presents, flowers, and cards to their mothers.
In olden times it was considered important for people to return to their home or "mother" church at least once a year. So each year in the middle of Lent, everyone would visit their "mother" church.
As the return to the "mother" church became an occasion for family reunions when children who were working away from home returned. (It was quite common in those days for children to leave home to work in service from ten years of age.)
The majority of historians think that it was this return to the "Mother" church which led to the tradition of children, particularly those working as domestic servants, or as apprentices, being given the day off to visit their mother and family.