[Docs] updated refrences to dynamic_date_formats

docs/reference/mapping/date-format.asciidoc

@@ -1,9 +1,11 @@
 [[mapping-date-format]]
 == Date Format
 
-When defining a `date` type, or when defining `date_formats` in the
-`object` mapping, the value of it is the actual date format that will be
-used to parse the string representation of the date. There are built in
+In JSON documents, dates are represented as strings. Elasticsearch uses a set
+of pre-configured format to recognize and convert those, but you can change the
+defaults by specifying the `format` option when defining a `date` type, or by
+specifying `dynamic_date_formats` in the `root object` mapping (which will
+be used unless explicitly overridden by a `date` type). There are built in
 formats supported, as well as complete custom one.
 
 The parsing of dates uses http://joda-time.sourceforge.net/[Joda]. The

docs/reference/mapping/types/object-type.asciidoc

@@ -126,7 +126,8 @@ stored and they are always indexed.
 Date fields are special since they are represented as a `string`. Date
 fields are detected if they can be parsed as a date when they are first
 introduced into the system. The set of date formats that are tested
-against can be configured using the `date_formats` and explained later.
+against can be configured using the `dynamic_date_formats` on the root object,
+which is explained later.
 
 Note, once a field has been added, *its type can not change*. For
 example, if we added age and its value is a number, then it can't be