No it doesn't require to be capitalized.
no
It should be --- Earth Day, Planet Earth.
Since 'day' is a common noun, you should only capitalize it if at the start of the sentence or part of a name/title (Eg: Graduation Day 2013).
You should capitalize it if it is a brand name.
No, you should not. You should only capitalize a word when it is at the start of a sentence or when it is a proper noun.
yes, surey!
no
In the salutation "Good day to you," you only need to capitalize the first word, "Good."
The phrase "Columbus Day" is the full name of a holiday. Therefore, both words should be capitalized.
It should be --- Earth Day, Planet Earth.
The last day of the Christmas season (January 9th) is the Feast of Baptism of the lord. If you have a advent scripture book this should be the day that it ends.
Yes, you always capitalize a day of the week.
Hercules is not a saint and has no feast day.
Yes, Memorial Day should be capitalized as it is a proper noun.
Feast of the Assumption of the Blessed Virgin Mary - this is a major feast day
The feast day of Saint Apollonia of Alexandria is on February 9.
The feast day of Saint Anastasia of Sirmium is on December 25.