You should always capitalize months and weekdays in English grammar. This is because they are proper nouns. A noun is the term we use for the names of people, places, things, and ideas. Nouns can be either common or proper.
Proper nouns are the names we give to specific people, places, things, and ideas. When we use them in writing, we always capitalize them:
Millions of people visit Yellowstone National Park every year.
The astronauts on Apollo 11 were Neil Armstrong, Michael Collins, and Buzz Aldrin.
Is the first day of the week Sunday or Monday?
My birthday is in October.
In English grammar, we consider months and weekdays specific things, so they are proper nouns, and we capitalize them.
Names of the Months
Do you know this rhyme to help you remember the number of days in each month? Each month has a specific name, so it’s capitalized:
Thirty days has September,
April, June, and November.
All the rest have thirty-one,
Except February, twenty-eight days clear,
And twenty-nine in each leap year.
Names of Weekdays
Did you ever watch Happy Days on TV? Do you remember the theme song lyrics by Gimbel and Fox?
“Sunday, Monday, happy days,
Tuesday, Wednesday, happy days,
Thursday, Friday, happy days,
Saturday, what a day,
Rockin’ all week with you.”
Each day has a specific name, making it a proper noun, so we capitalize it.
Common nouns are the names we give to unspecific people, places, things, and ideas. When we use them in writing, we capitalize them only sometimes.
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Take the Friends theme (Crane, Kauffman, Skloff, and Willis), which has the line:
“When it hasn’t been your day, your week, your month, or even your year.”
It doesn’t refer to specific days or months, so we don’t capitalize those nouns. You should only capitalize these words if they appear at the beginning of a sentence or in a title.
What About Seasons?
English grammar considers seasons common nouns, since they refer to a general period instead of a specific day or month. We, therefore, only capitalize seasons if using them in a title or at the beginning of a sentence:
The new school year starts in the fall.
The spring flowers were starting to bloom.
Winter is my favorite season.
You should always capitalize specific names of months and weekdays, such as “August” or “Tuesday,” because these are proper nouns. You should never capitalize generic terms, such as “week” or “summer” – unless they begin sentences or appear in a title – because they are common nouns.
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