Mother's Day is celebrated in many countries now. It is often celebrated in May, especially the second Sunday in May - this is the date in most of Europe and the US, and many other countries too including Singapore. In some Eastern European countries and Russia, Mother's Day isn't commonly celebrated; instead, these countries have a celebration on Women's Day, which is considered to give special importance to mothers.
The original Mothering Sunday comes from the UK and is held in March (in much of the Middle East it is also common to have Mother's Day in March). The British holiday is based on the Christian calendar and falls on the fourth Sunday in Lent, which in 2013 will be 10 March. It is said to have started with the old custom of visiting your original parish church (or mother church) at this time. Later it became the custom for girls and women working in domestic service to be given this day off to go and visit their mother and take her a cake.