Although it wasn't celebrated in the U.S. until 1907, there were days (honoring) mothers even in the days of ancient Greece. In those days, however, it was Rhea, the Mother of the gods that was given honor.
Later, in the 1600's, in England there was an annual (observance) called "Mothering Sunday." It was celebrated during June, on the fourth Sunday. On Mothering Sunday, the servants, who generally lived with their employers, were encouraged to return home and honor their mothers. It was traditional for them to bring a special cake along to celebrate the (occasion).
Many other countries of the world celebrate their own Mother's Day at different times throughout the year. Denmark, Finland, (Italy), Turkey, Australia, and Belgium celebrate Mother's Day on the second Sunday in May, as in the U.S.