Time Dimension - Cannot filter on 31 Dec 2000

I have a cube in Analysis Server 2005 with a time dimension. One of my
measures has data for the date 31 Dec 2000. If I 'filter' in the cube browser
on this date I get no data.

If I remove all measures and attempt to filter the Time dimension on 31 Dec
2000 it does not display a row for 31 Dec 2000. Instead it shows a row for 01
Jan 2001 which has become selected in the filter drop down.

So I created a fresh cube pointing at Northwind. Built a cube on the Orders
table and a Server time dimension. If I filter that time dimension on 31 Dec
2000 whilst running a SQL Profiler the MDXQuery is as follows...

CREATE SESSION
SET [Northwind].[{072EF838-5749-4389-A414-83361581E5F5}Pivot4Hier11] AS
'
VISUALTOTALS(
HIERARCHIZE(
{
[Time].[Date].[All],
[Time].[Date].&[2001-01-01T00:00:00]
}
)
)
'

Again 31 Dec 2000 has been replaced with 01 Jan 2001.

Is there some kind of date issue with 31 Dec 2000 or am I missing something?