Julia Ward Howe in 1861
Julia Ward Howe was the first to proclaim Mother's Day in 1870. Her Mother's Day Proclamation was a pacifist reaction to the American Civil War and the Franco-Prussian War. The modern holiday of Mother's Day was first celebrated in 1908, when Anna Jarvis held a memorial for her mother in America. 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's now celebrated all over the world.
In 1912, Anna Jarvis trademarked the phrases "second Sunday in May" and "Mother's Day", and created the Mother's Day International Association.
She was specific about the location of the apostrophe; it was to be a singular possessive, for each family to honor their mother, not a plural possessive commemorating all mothers in the world.
This is also the spelling used by U.S. President Woodrow Wilson in the law making official the holiday in the United States, by the U.S. Congress on bills, and by other U.S. presidents on their declarations.
Common usage in English language also dictates that the ostensibly singular possessive "Mother's Day" is the preferred spelling, although "Mothers' Day" (plural possessive) or "Mothers Day" (plural non-possessive) are sometimes used.As the American holiday was adopted by other countries and cultures, the date was changed to fit already existing celebrations honoring motherhood.
Mothering Sunday in the United Kingdom or, in Greece, the Orthodox celebration of the presentation of Jesus Christ to the temple (2 February). Mothering Sunday is often referred to as "Mother's Day" even though it is an unrelated celebration.
In some countries the date was changed to one that was significant to the majority religion, such as Virgin Mary day in Catholic countries. Other countries selected a date with historical significance, such as Bolivia using the date of a battle where women participated.