diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -3059,6 +3059,9 @@
         user = opts.get('user') or old.user()
         date = opts.get('date') or old.date()
 
+        # Parse the date to allow comparison between date and old.date()
+        date = util.parsedate(date)
+
         if len(old.parents()) > 1:
             # ctx.files() isn't reliable for merges, so fall back to the
             # slower repo.status() method
diff --git a/tests/test-amend.t b/tests/test-amend.t
--- a/tests/test-amend.t
+++ b/tests/test-amend.t
@@ -85,6 +85,14 @@
   nothing changed
   [1]
 
+  $ hg amend -d "0 0"
+  nothing changed
+  [1]
+
+  $ hg amend -d "Thu Jan 01 00:00:00 1970 UTC"
+  nothing changed
+  [1]
+
 Matcher and metadata options
 
   $ echo 3 > C