Capitalization: The Days Of The Week, The Months Of The Year, And Holidays (But Not The Seasons Used Generally)
Days, months, and holidays are always capitalized as these are proper nouns.
The maid comes on Tuesdays and Fridays.
My doctor’s appointment is on Monday afternoon.
Your birthday is in March, right?
Thanksgiving in November, Christmas in December, and New Years in January: North America has a lot of winter holidays.
The seasons aren’t capitalized unless they’re in a title or being used as a proper noun (such as when personified in creative writing).
My favorite season is autumn.
Many animals hibernate in the winter.
My favorite movement in Vivaldi’s The Four Seasons is Spring.
It’s that time of year again, when Winter blankets all creatures with somniferous snow and whispers to them, “Rest, children, rest.”