The days if the week each begin with a capital letter.
Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday
The months of the year are capitalized.
January, February, March, April, May, June, July, August, September, October, November, December
The names of holidays are capitalized.
Memorial Day, Mother's Day, Thanksgiving, Kwanzaa
Tip: The names of the seasons (spring, summer, autumn, and winter) are not capitalized unless they appear at the beginning of a sentence.