In the 12 hour clock, use lower case for am and pm and don’t use full stops. The Style Manual (see last post) recommends that because am and pm are always preceded by a numeral, they can be treated like other symbols associated with numbers which are unpunctuated. Put a space between the numeral and the am or pm, so the time is easier to read.
By the way, am is an abbreviated form of the Latin ante meridiem (meaning before midday or noon) and pm for post meridiem meaning after noon.
A full stop should be used to separate the hours from the minutes (not a colon which is common in American English).
To minimise confusion between midnight and noon, use 12 midnight (instead of 12 am, representing the start of the 24 hour day) and 12 noon (instead of 12 pm).
For times on the hour such as 11 am, there is no need to show the zeros (11.00 am) as it doesn’t add any meaning and makes it harder to distinguish between 11 am and times past the hour such as 11.30 am.
These guidelines reflect the trend towards minimal punctuation. Punctuation is used to help communicate clearly. If it doesn’t help, then leave it out.
The Style manual for authors, editors and printers is published by the Australian Government to provide guidance on preparing material for publication. While originally intended to provide advice for government publications, it is widely used as a reference work for effective communication.
The current Sixth Edition is a comprehensive reference of over 500 pages with five parts covering:
- planning the communication
- writing and editing
- designing and illustrating
- legal and compliance aspects of publishing
- producing and evaluating the product.
Part 2 on writing and editing is the heart of the manual and provides best practice advice on grammar, spelling, punctuation, abbreviations, lists and much more.
You don’t have to follow every recommendation in the Style manual, but it’s a great starting point to ensure clear and consistent communication.
Some practices have changed since the current edition was published back in 2002. When it is next updated, the new edition is likely to reflect trends towards minimal punctuation and include even more information on electronic publishing.
The Style manual is only available in hard copy and has a RRP of $44.95. A great resource for all writers and editors.