Science Museum - Atomic Clocks
- Talks about how different types of atomic clocks work, and the history of their invention.
- http://www.sciencemuseum.org.uk/onlinestuff/stories/atomic_clocks.aspx

US Library of Congress - How does an hourglass measure time?
- Answers questions about how an hourglass keeps time and what are the contributing factors determining how long an hourglass lasts.
- http://www.loc.gov/rr/scitech/mysteries/hourglass.html

Industrious Clock
- Clock using video of a hand drawing to display the time.
- http://yugop.com/ver3/stuff/03/fla.html

The Hourglass
- The University of Houston College of engineering, describes how an hourglass works and also provides interesting facts about this timekeeper.
- http://www.uh.edu/engines/epi1469.htm

The Galileo Project - Pendulum Clock
- Describes Galileo's work on pendulums and the pendulum clock.
- http://galileo.rice.edu/sci/instruments/pendulum.html

How Stuff Works: Time
- Complete five-part explanation of time and how it is measured, including information about clocks, time zones, and calendars.
- http://www.howstuffworks.com/time.htm

Discover - Time Machine
- Article explores a clock designed to keep accurate time for 10,000 years.
- http://www.discover.com/issues/nov-05/cover/

National Geographic Kids Magazine: Water Clock Experiment
- Demonstrates how water clocks can be used to keep time.
- http://www.nationalgeographic.com/ngkids/trythis/try10.html

A History of Time
- A two-part article that discusses physicist's evolving view of time.
- http://www-history.mcs.st-andrews.ac.uk/HistTopics/Time_1.html

On Time
- 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.
- http://americanhistory.si.edu/ontime/

When Does Daylight Savings Time Occur
- Explanation of when and why we have daylight savings time.
- http://www.logan.ws/articles/when_does_daylight_savings_time_occur.asp

Countdown
- Calculate the exact time in days, hours, minutes and seconds from now until your birthday or any other event.
- http://www.spiders.com/portfolio/demos/countdown/

NPR : 'Seize the Daylight'
- Talks about the complicated politics and curious history of daylight standard time.
- http://www.npr.org/templates/story/story.php?storyId=4572036

Local Times Around the World
- Find out what time it is anywhere in the world.
- http://www.timeanddate.com/worldclock/

World Time Converter
- Provides online times converter and brief information about GMT/UTC.
- http://www.gkindia.com/bitsol_time/

What Time Is It!
- 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.
- http://www.whattimeisit.com/

A Walk Through Time
- An illustrated history of timekeeping from ancient times to the present.
- http://physics.nist.gov/GenInt/Time/time.html

Time Travel
- Is time travel possible? See what Carl Sagan and Einstein had to say about time travel in this NOVA special.
- http://www.pbs.org/wgbh/nova/time/

Time
- Just how do we measure time and what has Greenwich England got to do with it?
- http://www.mrdowling.com/601-time.html

Making a Horizontal Sundial
- Learn how to make a sundial. Instructions are for beginners, intermediate, or advanced, and work for either the northern or southern hemispheres.
- http://www.lmsal.com/YPOP/Classroom/Lessons/Sundials/sundials.html

Making a Sun Clock
- Before there were clocks, people used shadows to tell time. Learn how to make your own sun clock!
- http://www.exploratorium.edu/science_explorer/sunclock.html

Make Your Own Star Clock
- Learn how to tell time by finding constellations in the night sky.
- http://www.lhs.berkeley.edu/StarClock/starclockprintout.html

Latitude and Longitude
- Introduction to latitude and longitude, a way of calculating exactly where you are anyplace on earth and a way to tell time.
- http://www-spof.gsfc.nasa.gov/stargaze/Slatlong.htm

International Standard Date and Time Notation
- International Standard ISO 8601 specifies numeric representations of date and time. It helps to avoid confusion caused by the many different national notations.
- http://www.cl.cam.ac.uk/~mgk25/iso-time.html

Daylight Saving Time
- Why do we use daylight savings time and who invented it?
- http://www.mrdowling.com/601-daylight.html