diff -r c9ce3999f76b -r 5152d59c147c src/ztfy/utils/schema.py
--- a/src/ztfy/utils/schema.py	Tue Nov 13 16:03:37 2012 +0100
+++ b/src/ztfy/utils/schema.py	Tue Nov 20 17:51:28 2012 +0100
@@ -20,7 +20,7 @@
 
 # import Zope3 interfaces
 from z3c.form.interfaces import IWidget
-from zope.schema.interfaces import ITextLine, IDecimal, IList
+from zope.schema.interfaces import ITextLine, IDecimal, IList, ITuple
 
 # import local interfaces
 
@@ -28,7 +28,7 @@
 from z3c.form.converter import BaseDataConverter, FormatterValidationError
 from zope.component import adapts
 from zope.interface import implements
-from zope.schema import TextLine, Decimal, List
+from zope.schema import TextLine, Decimal, List, Tuple, Date
 from zope.schema._bootstrapfields import InvalidValue
 
 # import local packages
@@ -111,6 +111,24 @@
 
 
 #
+# Dates range field
+#
+
+class IDatesRangeField(ITuple):
+    """Marker interface for dates range fields"""
+
+
+class DatesRangeField(Tuple):
+    """Dates range field"""
+
+    implements(IDatesRangeField)
+
+    def __init__(self, value_type=None, unique=False, **kw):
+        super(DatesRangeField, self).__init__(value_type=None, unique=False,
+                                              min_length=2, max_length=2, **kw)
+
+
+#
 # TextLine list field
 #