Windows aren't changing at night?

Code:

local houses = workspace.Houses

game.Lighting:GetPropertyChangedSignal("ClockTime"):Connect(function()
    if game.Lighting.ClockTime == 18 or game.Lighting.ClockTime >= 18 and not game.Lighting.ClockTime == 19 then
        for i, v in pairs(houses:GetDescendants()) do
            if v:IsA("Part") and v.Material == Enum.Material.Glass then
                v.Material = Enum.Material.Neon
                v.BrickColor = BrickColor.new("New Yeller")
            end
        end
    elseif game.Lighting.ClockTime == 6 or game.Lighting.ClockTime >= 6 and not game.Lighting.ClockTime == 7 then
        for i, v in pairs(houses:GetDescendants()) do
            if v:IsA("Part") and v.Material == Enum.Material.Glass then
                v.Material = Enum.Material.Glass
                v.BrickColor = BrickColor.new("Pastel Blue")
            end
        end
    end
end)

The problem is that nothing is changing.