Dates

Always use figures for dates and write them as day month year, with no commas:

The general election will be held on Thursday 7 May 2015.

Don't use "th", "st", and "nd" - just the number and the month:

The new semester begins Monday 12 January.

Include days of the week, unless it makes things confusing:

The lecture is scheduled for Tuesday 31 March.

Professor Wednesday Adams will be giving a lecture on 31 March.

For a range of dates, use figures and a dash (with no spaces):

11 July-16 September

Use figures for decades:

the 1960s

the swinging 60s

Write centuries in full for one to nine and figures for 10 and above:

21st century

fourth century BC

When written with figures, AD goes before the date and BC afterwards (both with no spaces:

AD2020

10,000BC