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. Seasons aren’t generally capitalized unless they’re personified.
The seasons aren’t capitalized unless they’re being used as a proper noun, such as when personified in creative writing or poetry. Consider the sentences below:
Generally speaking, the days of the week and months of the year are capitalized, but there are exceptions to this rule.