Dates, Time & Eras


At Middlebury, we express dates: month/day/year.

March 16, 1998
The meeting is on March 7 (not: March 7th, 7 March).
We will see you on the 13th of July.
October 7–17, 2011; October 7–November 5, 2011
Tickets are on sale, Wednesday, June 5, at the concert hall.

Note: See “Hyphens and Dashes” for more on en-dash use: An en dash is longer than a hyphen and is used between inclusive numbers, to show a range.

In a sentence, separate the day and year with commas:

The president was born on August 9, 1950, in a New York checker cab.

No comma is used when the month and year appear without a day:

The weather pattern changed in October 1998 for the better.


Cultural Periods

Some are lowercased; some are capitalized. Refer to Chicago Manual of Style or the dictionary.

romantic period; nuclear age; classical period; Victorian era; colonial period; Roaring Twenties; Ice Age; Middle Ages; Renaissance


Centuries and Decades

Spell out centuries, using the same numeral rules (spell anything lower than 10).

fourth-century art
life in the 21st century

Several options for identifying decades may be used:

1980s, 1960s; ’60s, ’80s; eighties, sixties

Note: no apostrophe between the year and s



Abbreviations for eras are set in full caps, with no periods:

AD “Anno Domini” (“in the year of the Lord”)
CE “of the common era” equivalent to AD
BC “before Christ”
BCE “before common era” equivalent to BC
BP “before the present”

AD precedes the year, the others follow it.

150 BC
AD 150

Commas are not used in dates with fewer than five digits.

3200 BC
10,500 BC


Time of Day

All of the following are acceptable—consistency is key; don’t vary the format within the same document or story:

Use numerals with AM and PM, and words with o’clock:

5 AM; five o’clock

Use small caps, or lowercased letters with periods:

a.m.; p.m.

Use numerals when the exact moment is important:

The train departs at 2:08 PM.

Other uses:

9:00 PM; 9 PM
noon; midnight

Note: There is no such thing as 12:00 a.m. or 12:00 p.m. because a.m. begins immediately after midnight and p.m. begins immediately after noon.

Showing ranges:

9:30 a.m.–10:30 p.m., or 9:30 AM to 10:30 PM
from 9 AM to noon  (do not use a dash to show range when also using “from”)

What are small caps? They are capital letters about three-quarters smaller than regular caps. Choose them from the font menu in Microsoft Word or from Word’s formatting palette.