[Zope] Incrementing with DateTime

[Colyn Brown]

I stumbled upon a strange occurrence when I incrementally add days
using the DateTime function. For some reason, on Sunday October 27 (it
has to be a Sunday) of any given year, when I try to add a day to it,
it only adds 23 hours instead of 24...causing the day to still be the
27th (with 23 hours added). Here is printed loop to illustrate what
I'm talking about:

2002/10/11 00:00:01 US/Mountain
2002/10/12 00:00:01 US/Mountain
2002/10/13 00:00:01 US/Mountain
2002/10/14 00:00:01 US/Mountain
2002/10/15 00:00:01 US/Mountain
2002/10/16 00:00:01 US/Mountain
2002/10/17 00:00:01 US/Mountain
2002/10/18 00:00:01 US/Mountain
2002/10/19 00:00:01 US/Mountain
2002/10/20 00:00:01 US/Mountain
2002/10/21 00:00:01 US/Mountain
2002/10/22 00:00:01 US/Mountain
2002/10/23 00:00:01 US/Mountain
2002/10/24 00:00:01 US/Mountain
2002/10/25 00:00:01 US/Mountain
2002/10/26 00:00:01 US/Mountain
2002/10/27 00:00:01 US/Mountain
2002/10/27 23:00:01 US/Mountain
2002/10/28 23:00:01 US/Mountain
2002/10/29 23:00:01 US/Mountain
2002/10/30 23:00:01 US/Mountain
2002/10/31 23:00:01 US/Mountain

This seems to happen on the last Sunday in October of any year. Weird.
Any input on this would help me out.

--colyn