diff --git a/AUTHORS b/AUTHORS
index 19b9b937b..06274dc7d 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -125,4 +125,5 @@ suggestions:
   Joe Holloway
   Peter Lewis
   Najmi Ahmad Zabidi
+  Philipp Woelfel
 
diff --git a/ChangeLog b/ChangeLog
index 6b8a2d620..fe7cf2486 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -237,6 +237,8 @@
    handling multiple arguments (thanks to Uli Martens).
  + Fixed bug #850, which failed when newline characters were in a modified task
    description.  They are now stripped (thanks to Aikido Guy).
+ + Fixed bug #851, which failed to recognize durations like '1day' when
+   filtering date attributes (thanks to Philipp Woelfel).
  + Fixed bug #856, which prevented filters on missing project from working
    (thanks to Michelle Crane).
  + Fixed bug #859, which used only one color for the 'ghistory.*' report
diff --git a/src/E9.cpp b/src/E9.cpp
index 3a9e42dad..0f774b6b7 100644
--- a/src/E9.cpp
+++ b/src/E9.cpp
@@ -38,6 +38,7 @@
 
 extern Context context;
 
+////////////////////////////////////////////////////////////////////////////////
 std::ostream& operator<< (std::ostream& out, const Arg& term)
 {
   out << term._value                        << "|"
@@ -115,6 +116,7 @@ void E9::eval (const Task& task, std::vector <Arg>& value_stack)
       }
 
       // TODO Not sure this is correct.
+      // TODO No longer sure why I was unsure in the first place.
       else if (arg->_raw == "-" && value_stack.size () < 2)
       {
         Arg right = value_stack.back ();
@@ -173,10 +175,25 @@ void E9::eval (const Task& task, std::vector <Arg>& value_stack)
       }
       else if (operand._type == Arg::type_date)
       {
+        // Could be a date, could be a duration, added to 'now'.
         operand._category = Arg::cat_literal;
-        operand._value    = (operand._raw != "")
-                            ? Date (operand._raw, _dateformat).toEpochString ()
-                            : "";
+        if (operand._raw != "")
+        {
+          if (Date::valid (operand._raw, _dateformat))
+            operand._value = Date (operand._raw, _dateformat).toEpochString ();
+
+          else if (Duration::valid (operand._raw))
+          {
+            Duration dur (operand._raw);
+            Date now;
+            now += (int)(time_t) dur;
+            operand._value  = now.toEpochString ();
+          }
+          else
+            operand._value = "";
+        }
+        else
+          operand._value = "";
       }
       else if (operand._type == Arg::type_duration)
       {
diff --git a/test/bug.851.t b/test/bug.851.t
new file mode 100755
index 000000000..7bec6a37e
--- /dev/null
+++ b/test/bug.851.t
@@ -0,0 +1,66 @@
+#! /usr/bin/perl
+################################################################################
+## taskwarrior - a command line task list manager.
+##
+## Copyright 2006-2012, Paul Beckingham, Federico Hernandez.
+##
+## Permission is hereby granted, free of charge, to any person obtaining a copy
+## of this software and associated documentation files (the "Software"), to deal
+## in the Software without restriction, including without limitation the rights
+## to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+## copies of the Software, and to permit persons to whom the Software is
+## furnished to do so, subject to the following conditions:
+##
+## The above copyright notice and this permission notice shall be included
+## in all copies or substantial portions of the Software.
+##
+## THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+## OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+## FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+## THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+## LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+## OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+## SOFTWARE.
+##
+## http://www.opensource.org/licenses/mit-license.php
+##
+################################################################################
+
+use strict;
+use warnings;
+use Test::More tests => 8;
+
+# Create the rc file.
+if (open my $fh, '>', 'bug.rc')
+{
+  print $fh "data.location=.\n";
+  close $fh;
+  ok (-r 'bug.rc', 'Created bug.rc');
+}
+
+# Bug 851: Filtering by due dates with ordinal and d/wks/etc. doesn't work
+qx{../src/task rc:bug.rc add yesterday due:-2days};
+qx{../src/task rc:bug.rc add tomorrow due:2days};
+my $output = qx{../src/task rc:bug.rc ls};
+like ($output, qr/yesterday/, "yesterday - task added");
+like ($output, qr/tomorrow/, "tomorrow - task added");
+
+$output = qx{../src/task rc:bug.rc list due.before:1d};
+like ($output, qr/yesterday/, "yesterday - found before:1d");
+unlike ($output, qr/tomorrow/, "tomorrow - not found before:1d");
+
+$output = qx{../src/task rc:bug.rc list due.after:1d};
+unlike ($output, qr/yesterday/, "yesterday - not found after:1d");
+like ($output, qr/tomorrow/, "tomorrow - found after:1d");
+
+# Cleanup.
+unlink qw(pending.data completed.data undo.data backlog.data synch.key bug.rc);
+ok (! -r 'pending.data'   &&
+    ! -r 'completed.data' &&
+    ! -r 'undo.data'      &&
+    ! -r 'backlog.data'   &&
+    ! -r 'synch.key'      &&
+    ! -r 'bug.rc', 'Cleanup');
+
+exit 0;
+