Numerically described periods are not capitalised:
- 21st century
- twenty-first century
- the nineteen-nineties
- 1990s with no apostrophe, not 1990's.
The preferred style is to use numerals rather than text.
- 27 November 1999, not 27th November 1999
- Monday 27 November 1995 (day, month, year with no punctuation)
- Antarctic summer 1992–93 (with an 'en' dash, not a hyphen)
- 1980s or early 2000s
- '50s and '60s
- in the twentieth century or in the 20th century, but 19th-century literature
- semester 1 or first semester
- semester 1 1996 or the first semester 1996
- World War I and World War II
- the Vietnam War and the French Revolution.
Also refer to Time of day.
For time spans, use an unspaced en dash for simple spans and a spaced en dash for complex spans. A space between the the number and the abbreviation (am or pm) should be retained. For example:
- 9–11 am, not 9am – 11am
- 9.30 am – 3 pm, not 9.30 am – 3.00 pm
- 10 am - 2 pm, not 10am-2pm
When referring to time of day in prose, use either from/to or between/and in place of the en dash. For example:
The lecture will be held from 9am to 10am on Wednesday.
The seminar takes place between 10am and 4pm on Friday.