The modern Mother's Day was created by 'ANNA JARVIS' as a day for each family to honor its mother, and it's now celebrated in many places around the world at different days.

One school of thought claims from a custom of mother worship in 'ancient greece' which kept a festival to Cybele, a great mother of Greek Gods.

The ancient Romans also had another holiday, MATRONALIA that was dedicated to JUNA, though mothers were usually given gifts on this day.

In 1912, ANNA JARVIS trademarked the phrases "Second Sunday in May" and created the Mother's Day International Association."
She was specific about the location of the apostrophe, it was a singular possessive for each family individually to honor thier mother, not a plural possessive, commemorating all mothers in the world.

This is also spelling used by US President Woodrow Wilson in the law making official the holiday in US by the Congress on bills and by other US Presidents on thier declaration.

A VERY HAPPY AND A HEALTHY MOTHER'S DAY TO ALL THE INDIVIDUAL MOTHERS

This is also spelling used by US President Woodrow Wilson in the law making official the holiday in US by the Congress on bills and by other US Presidents on their declaration.