Hi,
For landing the cabin lights are dimmed after the 'Final Cabin Secure' which is 10 mins to landing, they are then switched back on when we get onto stand.
As for take off they are dimmed again after 'Final Cabin Secure' after the crew have done demo and then switched back up after crew release - about 10-15 mins ater take off.
Hope this helps - this is just the way it is at my current airline.