Final answer:
A comma is necessary after the year in a date and after each element of an address except the last item. Commas should not be used around essential information. The use of commas can unify series for clarity.
Step-by-step explanation:
A comma is needed in sentences that include dates or addresses to clarify the separation of elements and improve readability. When a date is within a sentence, such as “Nobel Prize winner Toni Morrison died on August 5, 2019,” there is usually a comma following the year.
In the case of addresses, like in “The mailing address for the Smithsonian Institution is 600 Maryland Avenue SW, Washington, D.C., 20002,” commas are used to separate the street address, city, state, and zip code.
Commas with Numbers, Dates, Titles with Names, and Addresses are used to set off nonessential information or separate elements in a series.
For example, “During her trip to Europe, Erica visited Sweden, Norway, Denmark, and Holland.” This series use is also known as a serial (Oxford or Harvard) comma, which is generally included for clarity, though not always required.
A common comma error is using them improperly, like placing them around information that is essential to the meaning of a sentence.
For example, “Faculty who teach auto mechanics have requested updates to their lab” has no commas because the phrase “who teach auto mechanics” is essential to the meaning of the sentence.