Understanding English punctuation and grammar rules, including when to use commas in sentences, are crucial to writing English.

The idea of learning and understanding the many grammar rules in the English language can be daunting. There are many different uses of punctuation within sentences, and recognizing the difference between when to use them is important for written English. One common area for questions is comma punctuation, including how commas are to be used in regards to a date in a sentence.

Using Comma Punctuation in Written Dates

It is appropriate to use a comma after the date when you are separating the day of the month from the year in a written sentence. You can also put a comma after the year if the sentence calls for it. The rest of the sentence comes after the second comma.

Examples: 1) We are having the party on Oct. 4, 2011, in our backyard. 2) Her classes will begin Aug. 22, 2012, at the local community college.

Using Comma Punctuation with Definitive Dates Missing

Commas are not used if a part of a date is not present in a written sentence. Do not put a comma after the year if the day is missing. Also, don't use a comma after the date if the year is missing. The general rule of thumb is that if any part of the date is missing, leave off the comma.

Examples: 1) They were married in January 2011 in Las Vegas. 2) The date of their wedding was Jan. 14 of last year.

Using Comma Punctuation to Divide Clauses Including Dates

If you are writing a sentence with more than one clause that involves a two-part date, such as a month and day or a month and year, a comma comes after the first clause and before the second clause. This is true regardless of whether the date is at the end of the first clause or at the end of the sentence. Normal two-part date rules apply to the date in the written sentence.

Examples:

Comma after date: On March 3, she will perform in her first Broadway production.

No comma after year: He began his business studies at the beginning of his second semester, in January 2010.

Commas and Other Numbers

When discussing a number of years not directly related to a date, commas simply divide the clauses of a sentence. Do not place a comma after a number simply because it is a number.

Examples: 1) We have lived in our house for 30 years. 2) In five years, we will move to Arizona.