Can someone help me fix this?

ambient = game.Lighting.Ambient outdoorAmbient = game.Lighting.OutdoorAmbient timeOfDay = game.Lighting.TimeOfDay

if timeOfday >= 18:00:00 and <= 06:00:00 then ambient = 0,0,0 outdoorAmbient = 0,0,0 end

The output give me this: 09:24:18.273 - Workspace.Script:5: 'then' expected near ':'

I have no idea what this means, I would really appreciate it if someone explained this to me.