Need Help with a drop down list

Hi i have a form that uses a drop down list to change a date/time field that has been working for a long time but has recently stoped working.

The drop down list has 5 selections that change a date in the date/time field based off another date/time field untill recently has worked fine but now when selection 3-5 are selected the date shown is for example 1-14-1900.

Here is the code used

if (DropDownList1.rawValue == "1")then

          form1.Table2.Row3.DateTimeField1.formattedValue

elseif (DropDownList1.rawValue == "2")then

          form1.Table2.Row3.DateTimeField1.formattedValue

elseif (DropDownList1.rawValue == "3")then

          Num2Date((Date2Num(form1.Table2.Row3.DateTimeField1.formattedVal ue, "MMM DD, YYYY") + 14), "MMM DD, YYYY")

elseif (DropDownList1.rawValue == "4")then

          Num2Date((Date2Num(form1.Table2.Row3.DateTimeField1.formattedVal ue, "MMM DD, YYYY") + 21), "MMM DD, YYYY")

elseif (DropDownList1.rawValue == "5")then

          Num2Date((Date2Num(form1.Table2.Row3.DateTimeField1.formattedVal ue, "MMM DD, YYYY") + 25), "MMM DD, YYYY")

else null

endif

Any help would be appriciated.