mercurial/cmdutil.py

--- a/mercurial/cmdutil.py	Tue Sep 12 11:18:35 2017 -0400
+++ b/mercurial/cmdutil.py	Mon Sep 11 18:07:29 2017 +0200
@@ -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