pyderasn.py | 6 +++++-

diff --git a/pyderasn.py b/pyderasn.py
index 33ad909cbc6ead1d4a193e70127f4dc5bdc7a824874188df69d272ecf24e8457..ffaaa5650db0ddd1c28f992ef983e9025542c4207704858d93f367da23780536 100755
--- a/pyderasn.py
+++ b/pyderasn.py
@@ -4301,6 +4301,10 @@
        Only microsecond fractions are supported.
        :py:exc:`pyderasn.DecodeError` will be raised during decoding of
        higher precision values.
+
+    .. warning::
+
+       Zero year is unsupported.
     """
     __slots__ = ()
     tag_default = tag_encode(24)
@@ -4309,7 +4313,7 @@
     def _strptime(self, value):
         l = len(value)
         if l == LEN_YYYYMMDDHHMMSSZ:
-            # datetime.strptime's format: %y%m%d%H%M%SZ
+            # datetime.strptime's format: %Y%m%d%H%M%SZ
             if value[-1] != "Z":
                 raise ValueError("non UTC timezone")
             return datetime(