How Stuff Works: Time -- [ Teens/Mature Teens ] - Complete five-part explanation of time & how it's measured, including information about clocks, time zones, and calendars. Visit

Making a Horizontal Sundial -- [ Teens/Mature Teens ] - Learn how to make a sundial. Instructions are for beginners, intermediate, or advanced, & work for either the northern or southern hemispheres. Visit

Science Museum - Atomic Clocks -- [ Teens/Mature Teens ] - Talks about how different types of atomic clocks work, & the history of their invention. Visit

The Hourglass -- [ Kids/Teens ] - The University of Houston College of engineering, describes how an hourglass works & also gives interesting facts about this timekeeper. Visit

Local Times Around the World -- [ Teens/Mature Teens ] - Find out what time it's anywhere in the world. Visit

Latitude & Longitude -- [ Mature Teens ] - Introduction to latitude & longitude, a way of calculating exactly where you're anyplace on earth & a way to tell time. Visit

Time -- [ Kids/Teens ] - Just how do we measure time & what has Greenwich England got to do with it? Visit

On Time -- [ Kids/Teens/Mature Teens ] - Learn about the history of time measuring devices in this on line Smithsonian Institute exhibit. Page discusses how the accuracy of watches & clocks affected people's perception & usage of time. Visit

NPR : 'Seize the Daylight' -- [ Teens/Mature Teens ] - Talks about the complicated politics & curious history of daylight standard time. Visit

Countdown -- [ Kids/Teens/Mature Teens ] - Calculate the exact time in days, hours, minutes & seconds from now until your birthday or any other event. Visit

World Time Converter -- [ Teens/Mature Teens ] - Provides on line times converter & brief information about GMT/UTC. Visit

What Time Is It! -- [ Kids/Teens/Mature Teens ] - Gives the current time, synchronized by NIST. Close to 100 different time zones supported, as well as the ability to select the default time zone. Visit

Industrious Clock -- [ Kids/Teens/Mature Teens ] - Clock using video of a hand drawing to display the time. Visit

Discover - Time Machine -- [ Kids/Teens/Mature Teens ] - Article explores a clock designed to keep accurate time for 10,000 years. Visit

National Geographic Kids Magazine: Water Clock Experiment -- [ Kids/Teens ] - Demonstrates how water clocks can be often used to keep time. Visit

Time Travel -- [ Teens/Mature Teens ] - Is time travel possible? See what Carl Sagan & Einstein had to say about time travel in this NOVA special. Visit

A History of Time -- [ Teens/Mature Teens ] - A two-part article that discusses physicist's evolving view of time. Visit

US Library of Congress - How does an hourglass measure time? -- [ Kids/Teens/Mature Teens ] - Answers questions about how an hourglass keeps time & what are the contributing factors determining how long an hourglass lasts. Visit