A city with a bigger UTC offset is ahead; a smaller offset is behind. Find the difference between the two offsets, then add or take it away; the day changes when you cross midnight. A flight's arrival time is the departure time plus the flight, changed to the local time where it lands.
You call your cousin in London after school and wake her up at 5 am. A flight from Sydney lands in Los Angeles before it took off. Time zones explain both.
Each place keeps its own clock, set by its time zone. A zone is written as its offset from UTC (Coordinated Universal Time). This lesson uses the offsets for most of October: Sydney UTC+11 (daylight saving, from early October to early April; UTC+10 the rest of the year), Perth UTC+8, Tokyo UTC+9, London UTC+1 (until late October) and Los Angeles UTC−7 (until early November).
To change a time from one zone to another, find the difference between the offsets. A place with a bigger offset is ahead (later); a smaller offset is behind (earlier). Go by the offsets, not the map: Los Angeles is east of Sydney across the Pacific, but across the International Date Line, so it is 18 hours behind. Add or take away the difference, and change the day if you cross midnight. 24-hour time (21:30, not 9:30 pm) avoids mixing up morning and night.
For a flight: add the flight time to the departure time (in the departure zone), then change to the arrival zone.
Make your prediction first. Help opens once you've locked it in.
Is London ahead of Sydney or behind?
The slider sets Sydney's time; the other cities follow.
Was your prediction right? Now set Sydney to 14:00. What time is it in London?
Use the board. This ticks when you get there.
Here is the routine.
Now find Perth's time.
Read Kim's working. Is London ahead of Sydney or behind?
It is 14:00 in Sydney (UTC+11). What hour is it in Perth (UTC+8), in 24-hour time?
Kim finds the time in London. Click the line where her working goes wrong.
Sydney is 10 hours ahead of London.
9:00 + 10 hours.
Add the 14 hours on Sydney's clock first.
Then take away the 18 hours between Sydney and Los Angeles.
Perth is 3 hours behind Sydney.
Perth's 9:00 is Sydney's 12:00.
It is 9:00 am Monday in London. Set Sydney's time to match.
Use the board. This ticks when you get there.
A flight leaves Sydney at 22:00 on Friday and takes 14 hours. At what hour (24-hour time) does it land in Los Angeles (UTC−7)? Work it out, then check on the board.
Plan a call between Sydney and Perth that is between 9:00 and 17:00 in both cities. Set Sydney's time, then write the time in both.
Use the board. This ticks when you get there.
It is 10:00 in Sydney (UTC+11). What hour is it in Perth (UTC+8), in 24-hour time?
A train leaves at 08:45 and arrives at 17:20 the same day (one time zone). How many minutes is the trip?
It is 23:00 on Sunday in Perth (UTC+8). What hour is it in Sydney (UTC+11), in 24-hour time? (It is Monday there.)
A flight leaves Perth at 06:00 Perth time and lands in Sydney at 13:00 Sydney time. How many hours is the flight?
Then write both times for your flight, in 24-hour time with the day, as you would on a ticket.
The flight is 14 hours and Los Angeles is 18 hours behind Sydney.
Arrival (LA time) = departure + 14 − 18 = departure − 4.
A 14-hour flight leaves Sydney on Saturday. Choose a departure time so it lands in Los Angeles between 9:00 and 12:00 local time.
Use the board. This ticks when you get there.
Students move one city's time and watch the others follow, convert between time zones using UTC offsets, and plan flights and a call across zones (AC9M8M04, nodes 1 and 2). About 35 minutes.
Open the teacher guide: answers, solutions, slides and a worksheet.
Do the Run board yourself first.
The one idea: the city with the bigger offset is ahead; find the difference, add or take it away, and change the day at midnight. The common mistake is adding when the other city is behind (Kim's mistake).
The offsets in this lesson hold from 4 October to 25 October 2026: Sydney UTC+11 (daylight saving, from 4 October; +10 before), Perth +8, Tokyo +9, London +1 (British Summer Time ends 25 October), Los Angeles −7 (until 1 November). Go by offsets, not east and west on a map: Los Angeles is east of Sydney but behind, across the date line. Daylight saving changes them through the year, and not every Australian state uses it; check current offsets for real planning.
Wider: the International Date Line, why some zones are offset by half an hour (Adelaide, India), and planning a fair regular meeting for staff in several states and another country.
Ahead or behind. Ask students to compare the two offsets and say whose clock is later before they add or take away.
Stretch: Plan a video call between Sydney, Perth and London that falls between 8:00 and 21:00 for everyone. Is there one? Which city has to compromise most?
Support: A printed strip of 24-hour lines for each city, to slide against each other.
This completes AC9M8M04.
Where it leads: rates such as speed and time (Rates), and planning tasks in other subjects (Geography's time zones and the date line).