Consider them conquered territory. They used to be pagan days of celebration; now they're Christian days of celebration.
We have the freedom in Christ to celebrate Christmas if we choose. If you choose not to take advantage of that freedom and stay enslaved to the past, then that's your loss.
Who said so? You or G~d? Show me where He changed, please. Chapter and verse.
Ps 15:4 In whose eyes a vile person is contemned; but he honoureth them that fear the LORD. He that sweareth to his own hurt, and changeth not.