Dates and Time
Dates in text
Do not use st, nd, rd, or th following numerals in dates (i.e., April 1, not April 1st).
Days of the week
- Avoid abbreviation, except when needed in a tabular form.
- When you must abbreviate, use three letters with no periods (i.e., Sun, Mon, Tue, Wed, Thu, Fri, Sat).
Months of the year
- Do not abbreviate.
- When a phrase lists only a month and a year, do not separate the year with commas (e.g., March 1998 was a cold month. March 17 was a cold day of the month. March 5, 2009, is my wedding date.).
Lowercase spring, summer, fall, winter, and derivatives such as springtime, unless part of a formal name (e.g., The dance will occur in the spring, but Saint Peter’s Spring Fever is coming soon.)
- Decades are either spelled out and lowercased or expressed in numerals with no apostrophe between the year and the s (e.g., the nineties, the 1990s).
- You can abbreviate the year by replacing the first two digits with an apostrophe (e.g., the ’90s). If a font naturally curves the apostrophe, it must open to the left.
- Spell out centuries (e.g., the twenty-first century).
- Hyphenate when used as an adjective (e.g., twenty-first-century literature).
Minutes should always follow the hour, and time should always be written in the 11:00 a.m. format.
- Always lowercase and use periods.
- Avoid redundancies.
- Never use 12:00 a.m. or p.m. when using noon or midnight.
- Do not combine a.m. with in the morning, etc. (e.g., Meet me at 2:00 p.m., not Meet me at 2:00 p.m. this afternoon.).
- 10 – 11:00 a.m. is preferred rather than 10:00 a.m. – 11:00 a.m.
Avoid describing an event as annual until it has been held at least two successive years. You may note that sponsors plan to hold the event annually.
Biannual means twice a year or once every six months.
Biennial means every two years.
Bimonthly means every other month.
Semimonthly means twice a month.
Biweekly means every other week.
Semiweekly means twice a week.