It's time to clear up some confusion. Too many authors are all over the place when it comes to writing numbers, dates, years and times in their books. Find out if there are rules when it comes to writing numbers in fiction, exactly what the rules are, and what authors need to know to keep their work clean, readable, and formatted in a sensible way.
You Are Not Writing for a Newspaper
We all love AP style. It's an industry standard in newspaper writing, online writing and magazine writing of all kinds. It's a college course, and it's a requirement in English classes all over the nation.
It's also incorrect when you're writing a novel. When you're trying to figure out how to properly format your numbers, dates, years and times, the first thing you need to do is set fire to the AP style book. Do not follow these rules when you are writing prose for a novel -- fiction or non. The only time you'll need to know AP style if you write books, in fact, is if you plan to quote a newspaper article that appears in the book (but that's another post).
That said, you're also not writing for your college professor. So don't let me find out that you're using MLA style, either.
When it comes to writing a novel, you're not going to find a single, handy style guide that's going to help you out -- and I'm positive this is from where the trouble stems. Plenty of authors have published plenty of books on the topic, but I'm not about to recommend one of them because I don't own any them. I'm sure they're all wonderful. But when it comes to properly writing numbers, dates, years and times, you don't need an entire book to tell you how to do it. You only need to master a few very simple rules.
Writing Numbers in Novels
That subheading ins't there because I'm trying to be cute with my post. It's a reminder. When you are writing a book, you are writing -- so write it out. That's the first rule of properly formatting your text.
Again, because I can't stress this enough, you're not using AP style. So spell your numbers out in total, unless they're gigantic. Spell out everything above five, everything above nine, and don't forget to format your compound numbers. Whether it's fifty-seven or twenty-one, compound numbers are always written with a dash in-between and both numbers spelled out in full. Spell out large numbers like five million and three thousand. If you're writing a large and complicated number, however, say four thousand one hundred and eighty-four, it's going to read better and look better as 4,184. Always use the number comma in four-digit numerals.
Your fractions should likewise be fully written as compound numbers: Roughly one-half of the students in class were asleep by the time he finished explaining the Cuban Missile Crisis in full, bleak detail. How terrible does it look to write 1/2 instead? Isn't that the ugliest thing you ever saw? Now try reading it in a half-dozen indie books without running outside and screaming your head off. This is what I struggle with.
I have to put a lot of dates in my books, because there's a lot of detail about when people were born, when they died, and so on. Writing dates is very tricky, so when you're doing it make sure you're paying attention. My character can be born on January 17, but she can't be born on the 17th of Jan. You shouldn't ever use an abbreviation in your book, unless it's a common acronym (like PETA, or BA for Bachelor of Arts degree). It's not okay to write January as Jan unless you're specifically referencing something that appears in a text or an email (or something similar). It's not okay use 2nd, 11th, or any of the above. Write out second and seventeenth. It's just a few more letters, and it looks 100 percent better. You're writing a book...there's no rush.
Years should always be expressed as numerals except in very specific circumstances. It's cumbersome to write July 5, nineteen eighty-six, and looks silly. For years, it's always okay to use 1986, even in dialogue. It's also okay to use the year abbreviation in dialogue, for example '86 or '02, but make sure you use the apostrophe. Also, don't use the abbreviation in non-dialogue prose (example: Amber hadn't thought of Tim since '06, the year of the senior prom). Again, you're not in a hurry -- typing that extra digit isn't going to hurt you, and it looks better.
Many writers get this wrong -- not just in books, but everywhere I look. In prose, you really should be spelling out your decades (back in the seventies, Mr. Hamm experimented a little too much). But if you've just got to use the numerals, please do so correctly. It's '80s, never ever ever ever 80's. Why? because when an apostrophe precedes the s, you're usually showing possession. Are you saying that the number 80 has ownership of something, or are you referring to it? It's 1980s. It's never going to be 1980's.
If I'm a character in a book, I might celebrate tea time at four o'clock or even 4 o'clock. I might go out for my date at 8 PM or eight PM, or end up running late and not make it until 8:10 PM. What I'm not going to do is go to my date at eight-oh-five PM, unless I'm doing so inside dialogue. No other formatting is correct for times. If you're using numerals (ex. 8:10 PM), you must always use the colon. You don't have to capitalize PM and AM, though this is the accepted abbreviation. Some writers find the caps a little jarring, so you can switch to the lowercase pm if it really matters to you.
Be Consistent
Most importantly of all, be consistent. Even if you break all the rules above and do your own thing, do it consistently to keep your pages from looking like a hot mess. However you want to write your numbers, dates and times, always do it the same way. Otherwise, you look like you don't know what you're doing, and your readers are going to be confused.