diff -r 7e734ddad2e7 -r e1002cf9fe54 mercurial/util.py
--- a/mercurial/util.py	Wed Dec 01 17:50:49 2010 -0600
+++ b/mercurial/util.py	Wed Nov 24 19:31:43 2010 +0100
@@ -1116,6 +1116,8 @@
     # to UTC+14
     if abs(when) > 0x7fffffff:
         raise Abort(_('date exceeds 32 bits: %d') % when)
+    if when < 0:
+        raise Abort(_('negative date value: %d') % when)
     if offset < -50400 or offset > 43200:
         raise Abort(_('impossible time zone offset: %d') % offset)
     return when, offset