The modern holiday of Mother's Day was first celebrated in 1908, when Anna Jarvis held a memorial for her mother in Grafton, West Virginia. She then began a campaign to make "Mother's Day" a recognized holiday in the United States. Although she was successful in 1914, she was already disappointed with its commercialization by the 1920s. Jarvis' holiday was adopted by other countries and it is now celebrated all over the world. In this tradition, each person offers a gift, card, or remembrance toward their mothers, grandmothers, and/ or maternal figure on mother's day.
Here it is always the second Sunday in May.
In the United Kingdom it is Fourth Sunday in Lent,,therefore falling on March 10th this year and it will be March 30th next year.
I didn't know how it varied around the world
Mother's Day - Wikipedia, the free encyclopedia