日期加一天得到新的日期变量
比如　tt ="2012-10-31"　得到　tt1="2012-11-1"
[最优解释]
tt.AddDays(1)
[其他解释]
楼上正确

        Dim tt As Date = "2012-10-31"
        Dim tt1 As Date = tt.AddDays(1)
        MsgBox(tt1)