Fix docs on DateTime
They didn't say that they were optional.
In addition, make it more clear what a "Optional Variable" means.
@@ -267,6 +267,15 @@ prices. The values of ``Price`` field must be a positive float. If the value is
{'field': 'cost', 'type': 'Price'}
+Optional Variables
+------------------
+
+These variables aren't included in the core of dedupe, but are available to
+install separately if you want to use them.
+
+In addition to the several variables below, you can find `more optional
+variables on GitHub <https://github.com/search?q=org%3Adedupeio+dedupe-variable>`__.
+
DateTime
^^^^^^^^
@@ -303,9 +312,10 @@ and :code:`type`:
{'field': 'time_of_sale', 'type': 'DateTime'}
-
-Optional Variables
-------------------
+Install the `dedupe-variable-datetime
+<https://pypi.python.org/pypi/dedupe-variable-datetime>`__ package for
+``DateTime`` Type. For more info, see the `GitHub Repository
+<https://github.com/dedupeio/dedupe-variable-datetime>`__.
Address Type
^^^^^^^^^^^^
@@ -379,12 +389,6 @@ the ``FuzzyCategorical`` Type. For more info, see the `GitHub Repository
<https://github.com/dedupeio/fuzzycategory>`__.
-Other Optional Variables
-^^^^^^^^^^^^^^^^^^^^^^^^
-
-In addition to the several optional variables above, you can find `more optional
-variables on GitHub <https://github.com/search?q=org%3Adedupeio+dedupe-variable>`__.
-
Missing Data
------------
If the value of field is missing, that missing value should be represented as
