Teacher Downloads
Student Worksheet
Answer Key

Concepts Used
Measurement
Time
24 Hour clock
Integers
Working w. a formula

Grade level
Grades 5-8

Subject Areas
Math
Science

NCTM Standards
Properties of Numbers
Algebra
Measurement
Problem Solving
Connections
Representations
Technology

NETS*S
1c, 3a, 3c, 3d, 4c,
6a, 6b

Time Zone Problems


Objectives
  • Calculate time from one time zone to another.
  • Use a formula to calculate differences in time zones.

Lesson Description

Information can now be shared almost simultaneously anywhere across the world.  Advances in telecommunication and satellites link people with audio, video, and data transmissions within seconds.  Ironically, this speed can sometimes lead to confusion or a warped sense of time in the global setting.  Our Earth is still rotating in orbit around the Sun and so time zones is an important concept for students to understand.  Sunrise in Los Angeles is sunset in Moscow.  Time zones are a major consideration for global markets, businesses, and transportation.

This activity provides teachers and students with an interactive 3D model to calculate these differences in time.  Of course there are numerous websites or even wristwatches that can do these conversions for you, but here students will do the heavy lifting.  Time zones are often depicted in a two-dimensional graphic, so comprehension of the concept should be enhanced with the use of Google Earth.  Additionally, Google Earth has the ability to display sunlight on the Earth’s surface.  Important secondary objectives are that students are solving problems with a model and a formula.

A student worksheet that contains a variety of time zone problems and scenarios is included with the downloads below.  There are two ways these problems can be approached.  First, as one moves westward around the Earth, each time zone passed would result in a time one hour earlier than the previous.  An eastward movement brings a time one hour later than each previous time zone.  Students can use the Google Earth model to calculate times in this fashion, however, this can become more complicated with each time zone transcended.  Additionally, time zones are not marked in even divisions, nor do all zones represent an hourly increments.  Perhaps a better method of calculating the time would include a conversion formula.

The conversion formula relies on the knowledge of what time zone each site is located.  This is easily found in the Google Earth download in the form of icons that circle the globe.  Clicking on one of these icons will display the offset value from Coordinated Universal Time (UTC).  Since the time in zone A - the UTC offset value of zone A = time in zone B - the UTC offset value of zone B the following formula can be used...
time in zone A = time in zone B - UTC offset of zone B + UTC offset of zone A
or
A = B - UTCB + UTCA
This is truly a real world math topic that is worth exploring with students.  One avenue to pursue would be the history of recording time and how it has changed.  Another topic of discussion would be the irregularity of the time zone boundaries - “why don’t these follow lines of longitude?” or “what longitude value would the zones be if they were regular?”  Finally, you might want students to imagine changes that might take place in the future and the reasons for them.

Notes:
  • Real World Math’s Around the World in 40 Days is an extension of this lesson that includes elapsed time in the problems.
  • I’ve purposefully avoided the inclusion of Daylight Savings Time in worksheet’s problems since this adjustment is not used everywhere or all year long.  You can easily add this aspect to the problems if you wish.
  • Barnabu was the source I used for mapping the time zones in Google Earth.  You can find a link to their Google Earth KML below.  Their version was too good to use since it provides the current time for each time zone.  I thought this would be confusing for students.
  • Mapping the time zones was extremely difficult and time consuming.  Each zone is a polygon made up of hundreds of vertices.  No doubt, I may not have been precise enough in the bordering.  Please forgive me if I made an error in your location.  You can find the polygons in the Time Zone folder and edit them if needed, or add your location to the list of cities if you wish.
  • Finally, at the conclusion of the unit, I would share with students the variety of sources available for converting time.  Some of these are listed below.

Helpful links