From Kalinya --
Subject: question re fundamentals of writing

Hi MM>>
I would like to know how one handles the following:>>
1. Time – if we have a sentence such as: ‘His flight’s due to land at 7.45AM’ – how do we actually write the wretched thing? Do we say ‘ seven forty-five this morning’, or as it’s written in my original query? And on that point, is the ‘AM’ component of the time upper or lower case?>>
2. Numbers of things, be it quantities, measurement, age etc. Do we use the ‘spell it out if it’s less than ten and use numerals if it’s 10 or more’ rule?>>
3. Measurement – do we use imperial or metric? I live in Australia and we use metric – but what is best in fiction?>>
4. Currency / Monetary amounts - if we have to specify an amount of money in the body of our story – eg: ‘for the paltry sum of $30,000, Greased Lightning was his free and clear’, do we use the format used in my query, or do we spell it out as ‘...sum of thirty thousand dollars, Greased..’?>>
5.Dates be the of Birth or other significant dates included in body text – is is okay to use the 4 August 2012 format, or is it August 4th, 2012; or is it August fourth, 2012? >>
Thank you>>

According to The Chicago Manual of Style:
1. Time: numerals are used with zeros for even hours when exact times are emphasized. Chicago recommends lowercase a.m. and p.m. with periods and no space between the letters. Your example with the time of his flight should be written His flight’s due to land at 7:45 a.m. Notice the colon between the 7 and the 4. I see only a period in your example. Is that the way you do it down under?

If you aren’t talking about a scheduled flight, appointment, etc. use words.
Examples: Her day begins at five o’clock in the morning. When o’clock is used, the time should be spelled out.
The meeting continued until half past three. You aren’t emphasizing the time here. Use words instead of numerals.

2. Chicago likes to spell out numbers 1 – 100 and whole numbers – three thousand, four million. If the number begins a sentence, it is always spelled out. Whole numbers and fractions are usually given in numbers, but may be spelled out if they are short.

3. Measurement – use what you are comfortable using.

4. Sums of money of more than one hundred dollars are normally expressed by numerals. So your example of $30,000 is correct.

5. Dates – The format doesn’t matter. Use what you are comfortable with. Chicago advises not to use all numbers – 8-4-12, for instance.

I used The Chicago Manual of Style, “Chapter 9 Numbers” to answer your questions.