you have to split the datetime and then store it with your desired format like dd/MM/yyyy. then you can use this query with between but i have objection using this becasue it will search every single data on your database,so i suggest you can use datediff.
Dim start = txtstartdate.Text.Trim()
Dim endday = txtenddate.Text.Trim()
Dim arr()
arr = Split(start, "/")
Dim dt As New DateTime
dt = New Date(Val(arr(2).ToString), Val(arr(1).ToString), Val(arr(0).ToString))
Dim arry()
arry = Split(endday, "/")
Dim dt2 As New DateTime
dt2 = New Date(Val(arry(2).ToString), Val(arry(1).ToString), Val(arry(0).ToString))
qry = "SELECT * FROM [calender] WHERE datediff(day,'" & dt & "',[date])>=0 and datediff(day,'" & dt2 & "',[date])<=0 "
here i have used dd/MM/yyyy format.