Currency

When writing about currency, specify origin if not in Canadian dollars.

US$12
GB£9.99
JP¥100,000

Dates and Times

With dates, include the year after the date for clarification, unless it’s clear within the context of the piece or the posting.

All of the significant milestones were met in the latter half of last year with a few slight changes here and there. The most significant of all was the final day of the conference on May 25, 2012.

OR

All of the significant milestones were met in the latter half of 2012 with a few slight changes here and there. The most significant of all was the final day of the conference on May 25.

Write specific dates within the body of a text as follows, abbreviating the month.

Saturday, Sept. 19, 1998
Wednesday, Nov. 25

Do not change the order of construction, e.g. do not use "Saturday, 19 Sept."

For dates that are distant, omit the weekday.

Feb. 20, 2006

The months of March, April, May, June and July are never abbreviated because the words are so short. They are instead written out in full.

May 9, 1985
Thursday, July 3, 1997

When writing approximate dates within the body of a text, spell out the month in full.

During December (month only)

Avoid commas when you are referring to a specific month within a specific year.

Starting in September 1999 (no comma, month spelled out in full, year listed numerically.)
The target for completion of the project is August 1999.

When writing about decades, use numbers.

The 1920s, the 1980s, the ‘80s, the mid-1960s.

When writing about periods of time over years, write the numbers out in full using a hyphen not a slash.

1985-1990 (not ‘85-‘90)
2000-2001 (not 2000-‘01 or 2000/2001)

When writing about centuries, as with numbers spell out the first nine as words, and use digits for 10 and above.

the fifth century
the 19th century

Hours are written numerically with no zeros. Do not capitalize or use periods with am and pm.

9am (not 9:00am) 11pm but 11:45pm
noon (not 12 noon. The 12 is redundant.)

A range of times is written using the word "to" in text, but with a hyphen in tables.

The reception is scheduled from 8 to 11pm
Reception, 8-11pm

The above rules for dates and times apply within the body of text. In calendars, tables, forms or graphs where space is extremely tight, short forms and figures can be used.

Nov. ‘98 Dec. ‘98 Jan. ‘99

Metric

Shorten but do not punctuate metric symbols. Metre is m, kilometre is km, kilogram is kg, Celsius is C, metric tonne is t, hour is h. Only Celsius is capitalized as C.

He drove 10 km to the store.
The weather was a sunny 23 C on Wednesday.

Keep a space between the number and the symbol.

10 km (not 10km)

Use a hyphen when indicating a metric quantity as an adjective.

a 10-kilogram sack (Note that the quantity is spelled out in this case, when the metric term is part of an adjective.)

Numbers

Write the numbers one to nine as words. The same goes for first. . .ninth.

Write the numbers 10 and up as numerical figures.

3,500 26 99th 10th

When the number is four digits or longer, separate with commas rather than spaces or periods.

100,000 not 100 000 or 100.000
There are 1,200 students.
A $430,000 grant

For large numbers, it is better to use words or a combination of words and numbers. Write 1.4 million rather than 1,400,000. Write one million rather than 1,000,000.

For the plural of numbers, including decades, do not use an apostrophe before the "s".

The 1960s were exciting.
Give me all the 10s and 20s.

Percentages

Write out percentages.

Twenty percent (not 20%).