--- a/mercurial/util.py	Mon Apr 04 00:05:41 2011 +0200
+++ b/mercurial/util.py	Mon Apr 04 00:23:21 2011 +0800
@@ -1222,9 +1222,13 @@
     if not date:
         raise Abort(_("dates cannot consist entirely of whitespace"))
     elif date[0] == "<":
+	if not date[1:]:
+            raise Abort(_("invalid day spec. use '<{datetime}' "))
         when = upper(date[1:])
         return lambda x: x <= when
     elif date[0] == ">":
+	if not date[1:]:
+            raise Abort(_("invalid day spec. use '>{datetime}' "))
         when = lower(date[1:])
         return lambda x: x >= when
     elif date[0] == "-":