"Busy people need to keep track of time. A clock is used to measure seconds, minutes, and hours. Learn about different types of clocks and the history of clocks in 'Clock.'"--Back cover.
A calendar can help people to count how long it is until their birthday. Calendars measure days, weeks, months, and years. Learn about different types of calendars and the history of measuring days, weeks, months, and years in "Calendar".
Simple text and photographs introduce clocks, including the different types and the history of measuring seconds, minutes, and hours. Includes online content that contains weblinks, audio and video clips, activities, and other features.
