The Everyday History series explains in a clear and interesting way how different aspects of daily life have changed over the centuries. Each title guides the reader through time, showing important discoveries and changes that have resulted in the world, as we know it today. How did people measure time before there were any clocks? Who invented our calendar? What are time zones? What is jet lag? These questions and many others are answered in Telling the Time. Where did Stone Age people put their rubbish? How do you keep a dirt-floor clean? When was the vacuum cleaner invented? How will houses be cleaned in the future? These questions and many others are answered in Cleaning the House.