Commas are good, all-purpose separators. They won’t keep you and your worst enemy apart, but they do a fine job on addresses and dates — especially when items that are usually placed on individual lines are put next to each other on the same line.

How to punctuate addresses in your writing

Where are you from? Jill is from Mars. Belle is from a small town called Venus. Here’s her (fictional) address, the way you see it on an envelope:

Ms. Belle Planet
223 Center Street
Venus, New York 10001

In the body of a letter, you can insert an address in envelope form like this:

Please send a dozen rockets to the following address:
    Ms. Belle Planet
    223 Center Street
    Venus, New York 10001

The introductory words (Please send a dozen rockets to the following address) end with a colon ( : ) if they express a complete unit of thought. If the introductory words leave you hanging (Please send a dozen rockets to, for example), don’t use a colon.

If you put Belle’s address into a sentence, you have to separate each item of the address, as you see here:

Belle Planet lives at 223 Center Street, Venus, New York 10001.

Notice that the house number and street are not separated by a comma, nor are the state and zip code.

If the sentence continues, you must separate the last item in the address from the rest of the sentence with another comma:

Belle Planet lives at 223 Center Street, Venus, New York 10001, but she is thinking of moving to Mars in order to be closer to her friend Jill.

If there is no street address —just a city and a state — put a comma between the city and the state. If the sentence continues after the state name, place a comma after the state.

Belle Planet lives in Venus, New York, but she is thinking of moving to Mars.

Commas also separate countries from the city/state/province:

Roger lives in Edinburgh, Scotland, near a large body of water. His brother Michael just built a house in Zilda, Wisconsin.

How to punctuate written dates

The rules for placing commas in dates aren’t very stable these days. What was once carved into stone is now sometimes viewed as old-fashioned. To make matters even more complicated, writers from different areas (science, literature, and the like) favor different systems. If you’re writing for publication, check with your editor about the publisher’s preferred style.

If the date is alone on a line (perhaps at the top of a letter), these formats are fine:

September 28, 2060 (traditional)
Sept. 28, 2060 (traditional)
28 September 2060 (modern in the United States, traditional in many other countries)

When dates appear in a sentence, the format changes depending upon how traditional you want to be and how much information you want to give:

On September 28, 2060, Lulu ate several thousand gummy candies. (Traditional: commas separate the day and year and the year from the rest of the sentence.)
In October, 2060, Lulu gave up sugary snacks. (Traditional: a comma separates the month from the year and the year from the rest of the sentence.)
Lulu pigs out every October 31. (Timeless: both the traditional and modern camp omit commas in this format.)
In October 2060 Lulu suffered from severe indigestion. (Modern: no commas appear.)
Lulu visited a nutritionist on 20 October 2060. (Modern: no commas appear.)