Try this in WebAccess: in Week View or Day View create an appointment on a Saturday (has to be Saturday and no other day) after about 6pm, best 11pm. It is not shown, just like it does not exist. Before 6pm it seem to work fine. Only when you switch to Month View you see the hidden appt. Before SP1 Sunday had this problem and as far as I remember it was first few hours on Sunday that did not work. Looks like there is a problem with date filtering, with problematic few hours depending I guess on a timezone where you are and maybe in relation to the server timezone. Apparently there was an attempt to fix the problem, but it just got bumped to another day. In Week View the week starts from Sun and ends on Sat, so there was/is a problem at those boundary days. In Day View, well, the whole day is a boundary day.