What Region have you selected under Regional and Language Options in the
Control Panel?
The VBA Developer's Handbook (by Getz and Gelbert) states:
"Online help indicates that you can pass a second parameter to WeekDay,
indicating the first day of the week. In many countries, Monday is
considered the first day of the week, so most of the VBA date functions
allow you to specify what you consider to be the first day of the week. If
you don't specify a value, VBA uses the Windows setting for your local
country. If you specify a constant (vbSunday through vbSaturday) for this
parameter, VBA treats that day as the first day of the week and offsets the
return value accordingly."
http://msdn.microsoft.com/library/en-us/dnvbadev/html/pullingpiecesapart.asp
Unfortunately, I can't find details anywhere as to what the default is for
each Region.
Randy Birch shows how to determine the setting in
http://vbnet.mvps.org/code/locale/localedates.htm (Obligatory Warning:
Randy's site is aimed at VB programmers. Because there are significant
differences between the controls available for forms in VB and in Access,
not all of his samples can be ported directly to Access. At a quick look,
though, this particular one should be fine)
There is a iFirstDayOfWeek key in the registry under HKCU\Control
Panel\International, but I don't know what the possible values are (mine's
currently set to 6!)