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

Daylight Saving Time [ Teens/Mature Teens ] - Why do we use daylight savings time and who invented it?

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

The Galileo Project - Pendulum Clock [ Teens/Mature Teens ] - Describes Galileo's work on pendulums and the pendulum clock.

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

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

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

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

International Standard Date and Time Notation [ Mature Teens ] - International Standard ISO 8601 specifies numeric representations of date and time. It helps to avoid confusion caused by the many different national notations.

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

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

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

Making a Sun Clock [ Kids/Teens ] - Before there were clocks, people used shadows to tell time. Learn how to make your own sun clock!

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

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

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

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

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

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

A Walk Through Time [ Teens/Mature Teens ] - An illustrated history of timekeeping from ancient times to the present.

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.

When Does Daylight Savings Time Occur [ Teens/Mature Teens ] - Explanation of when and why we have daylight savings time.

World Time Converter [ Teens/Mature Teens ] - Provides online times converter and brief information about GMT/UTC.