I've been using the Calendar tag since zope 2.1.6. In the process of upgrading to Zope 2.4.3 I found the calendar tag does not work anymore. If I try to edit a date property, I get a Bad Request error, value: Invalid or duplicate property id. Traceback see below. I've been experimenting a bit and created an example faithfully following the Jon Udell How-to. I imported this example in different versions of zope. The incompatibility with the calendar tag gets to the surface somewhere after 2.2. Did nobody else experience this? tiv,cb Traceback (innermost last): File D:\Zope\243\lib\python\ZPublisher\Publish.py, line 223, in publish_module File D:\Zope\243\lib\python\ZPublisher\Publish.py, line 187, in publish File D:\Zope\243\lib\python\Zope\__init__.py, line 226, in zpublisher_exception_hook (Object: index_html) File D:\Zope\243\lib\python\ZPublisher\Publish.py, line 171, in publish File D:\Zope\243\lib\python\ZPublisher\mapply.py, line 160, in mapply (Object: editCalendarProperty) File D:\Zope\243\lib\python\ZPublisher\Publish.py, line 112, in call_object (Object: editCalendarProperty) File D:\Zope\243\lib\python\Shared\DC\Scripts\Bindings.py, line 324, in __call__ (Object: editCalendarProperty) File D:\Zope\243\lib\python\Shared\DC\Scripts\Bindings.py, line 354, in _bindAndExec (Object: editCalendarProperty) File D:\Zope\243\lib\python\Products\PythonScripts\PythonScript.py, line 363, in _exec (Object: editCalendarProperty) (Info: ({'script': <PythonScript instance at 01BE2670>, 'context': <DTMLMethod instance at 01BDDD40>, 'container': <Folder instance at 01BD3D20>, 'traverse_subpath': []}, (), {}, None)) File Script (Python), line 5, in editCalendarProperty (Object: guarded_getitem) File D:\Zope\243\lib\python\OFS\PropertyManager.py, line 320, in manage_addProperty (Object: Agenda) File D:\Zope\243\lib\python\OFS\PropertyManager.py, line 243, in _setProperty (Object: Agenda) Bad Request: (see above)