The Lessons of the Past can Prepare us for the Future
While etiquette changes and evolves over time, some things do remain remarkably constant. The social expectations that have been the most durable for generations provide a strong framework for understanding how to support relationships. You will find many examples like this here.
The manners that change and evolve over time also teach us things and have the power to reveal what is essential and requires change from us. It can also just be fun (if you are an etiquette geek like we are) to look back at what used to be expected with the understanding and perspective that only the passage of time can provide. You will also find information on anacranistic manners like these from other times and eras.