diff -r 044dc196ec8a -r d3668ecd9137 src/ztfy/utils/timezone/schema.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ztfy/utils/timezone/schema.py	Wed Jun 20 16:29:53 2012 +0200
@@ -0,0 +1,57 @@
+### -*- coding: utf-8 -*- ####################################################
+##############################################################################
+#
+# Copyright (c) 2008-2010 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+
+__docformat__ = "restructuredtext"
+
+# import standard packages
+import pytz
+
+# import Zope3 interfaces
+from zope.schema.interfaces import IChoice, IVocabularyFactory
+
+# import local interfaces
+
+# import Zope3 packages
+from zope.interface import implements, classProvides
+from zope.schema import Choice
+from zope.schema.vocabulary import SimpleTerm, SimpleVocabulary
+
+# import local packages
+
+
+class TimezonesVocabulary(SimpleVocabulary):
+
+    classProvides(IVocabularyFactory)
+
+    def __init__(self, *args, **kw):
+        terms = [SimpleTerm(t, t, t) for t in pytz.all_timezones]
+        super(TimezonesVocabulary, self).__init__(terms)
+
+
+class ITimezone(IChoice):
+    """Marker interface for timezone field"""
+
+
+class Timezone(Choice):
+    """Timezone choice field"""
+
+    implements(ITimezone)
+
+    def __init__(self, **kw):
+        if 'vocabulary' in kw:
+            kw.pop('vocabulary')
+        if 'default' not in kw:
+            kw['default'] = u'GMT'
+        super(Timezone, self).__init__(vocabulary='ZTFY timezones', **kw)