The majority of countries celebrate Mother’s Day in May.
May is the dominant month because many countries adopted the American observance promoted by Anna Jarvis. In the United States, Mother’s Day falls on the second Sunday of May, a pattern also used by countries including Canada, Australia, Japan, India and South Africa. Other nations use fixed May dates or different Sundays in the month.
The answer is sometimes confused by Mothering Sunday in the United Kingdom and Ireland, which takes place on the fourth Sunday of Lent and therefore usually falls in March. Several countries also observe the holiday in March, October, December or another month because of religious, political or national traditions.
May is therefore the best general answer, although Mother’s Day has no single worldwide date. The specific day varies by country, while May remains the most common month internationally.