Chicago Author-date Style
The Chicago Author-date style apes the Harvard Referencing system, again with minor differences. Whereas the Chicago Footnote System is generally used in the arts, humanities and social sciences, the Chicago Author-date style is more commonly used across the "natural' sciences, although Biologists also use the Vancouver Style (see a later blog entry for more on this). However, large differences exist between the Chicago Footnote System and the Chicago Author-date style, so make sure you've selected the right one. This blog entry should hopefully help.
Intext references are used in addition to providing footnotes and a bibliography, slightly different from the Harvard System which dispenses with the footnotes altogether. An example of an intext reference would be (Bodkins 2012, 123). The only difference between the Chicago Author-date style and the Harvard System is that the comma is removed after the surname and the "p.' is also omitted.
Adapt the Bibliography
Again there are only minor differences with how the Chicago Author-date style is laid out in the bibliography compared with the Harvard System.
Peter Bodkins. How To Reference Correctly. London: Fictitious Publishing. 2012.
Firstly, the name is listed first-name followed by Surname, and the date is listed at the end of the reference instead of after the name.
Similarly, other minor changes exist depending on which source is` being referenced. For example, when referencing a journal article, the title is placed in quotation marks and the title of the publication is not italicised. The "p.' to denote the page number is also omitted.
Peter Bodkins. 2012. "How to Reference Correctly". Fictitious Journals Quarterly, 10 (2), 123.
Also note that, unlike with references for books, the date follows the author's name instead of being placed at the end of the reference.
It's unlikely but not impossible that you will have to switch between using similar styles such as the Chicago Author-date System and the Harvard Referencing system if your degree spans more than one discipline. If this happens, pay particular attention that you're using the right one. It's unlikely you will lose many marks, if any, should you replace one similar system with another; however, you will likely loose marks if you combine the two and create your own system of referencing!
The link to the guide in the last blog entry, http://www.chicagomanualofstyle.org/16/ch14/ch14_toc.html gives an overview of both the Chicago Footnote Style and the Chicago Author-date Style – it's important to understand which one you've been asked to use as key differences exist between both styles. If in doubt, ask your lecturer or a member of the library staff. Also be aware that advice given online can be conflicting – for example some guides advise placing dates in brackets, whereas others advise using a full stop – don't get bogged down too much in this – just remember to always be consistent with how you lay out your intext references, your footnotes and your bibliographies.