Numerals, Fractions, and Dates Punctuation - CSS Typography | CSS: Presentation Layer

Compound numerals from twenty-one to ninety-nien are written with hyphens:

France is divided into ninety-six departments.

Mozart was only thirty-five years old when he died.

Note no additional hyphens are used in writing larger numbers:

A leap year has three hundred and sixty-six days.

The maximum possible score with three darts is one hundred and eighty.

Typically in formal writing, the numerals from one to twenty are always written out. Larger numbers, however, can be written with digits.

When writing a four-digit numeral in digits, other than a date, American usage is to never use a commma, however British usage does:

American: 2000 years, 4700 people.

British: 2,000 years, 4,700 people.

A number that has five or more digits always takes one or more commas.

There are exceptions for addresses and other special cases in which numerals are always written with digits.

I lived for ten years at 19 Dryden Drive in Poquoson, va.

Typically bad style to start a sentence with a numeral.

Fractions are always written with a hyphen:

Almost three-fourths of the earth's surface is water.

More than one-half of babies born are male.

Note: the following fraction use case, where the phrase one half is not a fraction:

One half of me wants to take the job while the other half doesn't.

In formal writing, always write fractions out; do not do this:

Almost ¾ of the earth's surface is water.

Commas are typically placed after the year when writing dates

It was on 18 April, 1775, that Paul Revere made his famous ride.

On December 7, 1941, the Japanese attacked Pearl Harbor.

She died on the last day of November, 1843.

British usage writes a date in day-month-year- fashion (23 March), while American usage is month-day-year fashion (March 23). This can cause serious internationalization problems, and its most likely best to use the international date dormat of year-month-date (2013 Mar 15).