Fixed #2443 -- Added DurationField.

A field for storing periods of time - modeled in Python by timedelta. It
is stored in the native interval data type on PostgreSQL and as a bigint
of microseconds on other backends.

Also includes significant changes to the internals of time related maths
in expressions, including the removal of DateModifierNode.

Thanks to Tim and Josh in particular for reviews.

1 files changed, 17 insertions, 0 deletions

diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt
index 2429406d68..203241ae5f 100644
--- a/docs/ref/models/fields.txt
+++ b/docs/ref/models/fields.txt
@@ -542,6 +542,23 @@ The default form widget for this field is a :class:`~django.forms.TextInput`.
     :class:`FloatField` and :class:`DecimalField` classes, please
     see :ref:`FloatField vs. DecimalField <floatfield_vs_decimalfield>`.
 
+``DurationField``
+-----------------
+
+.. versionadded:: 1.8
+
+.. class:: DurationField([**options])
+
+A field for storing periods of time - modeled in Python by
+:class:`~python:datetime.timedelta`. When used on PostgreSQL, the data type
+used is an ``interval``, otherwise a ``bigint`` of microseconds is used.
+
+.. note::
+
+    Arithmetic with ``DurationField`` works in most cases. However on all
+    databases other than PostgreSQL, comparing the value of a ``DurationField``
+    to arithmetic on ``DateTimeField`` instances will not work as expected.
+
 ``EmailField``
 --------------