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Dates and time

office of university communications


When citing dates, use numerals, not ordinal numbers. Do not abbreviate months.

August 5 was a hot day.

When using month-day-year, commas are used both before and after the year.

On May 17, 2001, the University held a celebration at Bapst Library.

Do not place a comma between the month and the year when the day is not mentioned.

Boston College’s May 2007 commencement brought together hundreds of people.


When citing the exact time, or when using a.m. or p.m., use numerals.

7:00 p.m., 7:30 p.m.

Write a.m. and p.m. in lowercase, with a period between the letters*.

a.m., p.m.

*The exception to the rule above is when writing in small caps, no period is placed between the letters.

9:00 am, 3:00 pm

Use noon for 12:00 p.m. and midnight for 12:00 a.m. In the beginning of a sentence, capitalize noon and midnight.

When listing start to end times, use an en dash

2:00–4:00 p.m.

Centuries and decades

Decades are either spelled out and lowercased or expressed in numerals. No apostrophe appears between the year and the s. You can abbreviate the year by replacing the first two digits with an apostrophe.

That was popular in the 1920s.

The nineties

The 1980s and 1990s (or ’90s)

Noun: the twentieth century
Adjective: twentieth-century literature