Clarify 'time zone' in a Specific words section (#1352)

* Clarify 'time zone' in a Specific words section

* Use a reference that matches the section title

* mention markup use for timezone

Author: nedbat

documentation/style-guide.rst

@@ -54,10 +54,15 @@ starting it with a lowercase letter should be avoided.
 Many special names are used in the Python documentation, including the names of
 operating systems, programming languages, standards bodies, and the like. Most
 of these entities are not assigned any special markup, but the preferred
-spellings are given here to aid authors in maintaining the consistency of
-presentation in the Python documentation.
+spellings are given in :ref:`specific words` to aid authors in maintaining the
+consistency of presentation in the Python documentation.
 
-Other terms and words deserve special mention as well; these conventions should
+.. _specific words:
+
+Specific words
+==============
+
+Some terms and words deserve special mention. These conventions should
 be used to ensure consistency throughout the documentation:
 
 C API
@@ -79,6 +84,12 @@ reST
    used to produce Python documentation.  When spelled out, it is
    always one word and both forms start with a lowercase 'r'.
 
+time zone
+   When referring to a Python term like a module, class, or argument spell it
+   as one word with appropriate markup (for example, ``:mod:`timezone```).
+   When talking about the real-world concept spell it as two words with no
+   markup.
+
 Unicode
    The name of a character coding system. This is always written
    capitalized.