Grandparents’ Day or National Grandparents’ Day is a secular
holiday celebrated in various countries; it is celebrated to show
the bond between grandparents and grandchildren.

National Grandparents Day is a secular holiday celebrated in the US and the
United Kingdom since 1978 and officially recognized in a number of countries 
on various days of the year, either as one holiday or sometimes as a separate
Grandmothers’ Day and Grandfathers’ Day, for the first time Grandma’s Day
was celebrated in Poland in 1965.