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4 to 5 Nov 2026
Home › Sequences & Finance › Time Zones
Unit 3

🌏 Time Zones

Work out what time it is anywhere in the world, and calculate flight arrival times across time zones. One simple rule runs everything: East = add, West = subtract.

What even is this? The Earth is divided into time zones based on how far east or west you are from a reference line called UTC. Every place has an offset, like +10 or −5, that tells you how many hours ahead or behind UTC it is. Converting between time zones is just adding or subtracting that difference.
If you only do one thing Convert through UTC: take off one offset to reach UTC, add the other to reach the target zone. Watch for crossing into the next day.

The 10-minute version

Low energy? Do just this and you have still won the day. Zero is the only fail.

The one move: read the first formula box and the first worked example above, then do Practice Question 1. Screenshot the win for Nat and stop there.

📺 Watch it explained

Four short ways in. The 🎬 cards are waiting on Nat's videos, and each has a ready-to-read film script tucked underneath. 🖨️ Prefer printable notes? 4 styles here.

1. UTC, The World's Reference Clock

UTC (Coordinated Universal Time) is the world's reference time. It doesn't change for daylight saving. Every time zone is defined as an offset from UTC, written as UTC+ (ahead) or UTC− (behind).

Think of UTC as the clock at the centre of the world. If you're in Australia, you're ahead of UTC, so you add hours. If you're in the USA, you're behind UTC, so you subtract hours.

The One Rule to Remember

⬆️ East
Add hours
Higher UTC offset = further east = later time
⬇️ West
Subtract hours
Lower UTC offset = further west = earlier time
2. Time Zones You Need to Know
−8 LA −5 New York 0 London (UTC) +4 Dubai +9 Tokyo +10 Brisbane/AEST ← west = subtract east = add → ⭐ reference
City / RegionStandard offsetNotes
Brisbane / QLDUTC+10AEST, no daylight saving
Sydney / MelbourneUTC+10 / UTC+11AEST in winter, AEDT (daylight saving) in summer
AdelaideUTC+9:30ACST, half-hour offset!
PerthUTC+8AWST, 2 hours behind Brisbane
TokyoUTC+9Japan Standard Time, no daylight saving
DubaiUTC+4Gulf Standard Time
LondonUTC+0GMT in winter, BST (UTC+1) in summer
New YorkUTC−5EST in winter, EDT (UTC−4) in summer
Los AngelesUTC−8PST in winter, PDT (UTC−7) in summer
3. Converting Between Time Zones

There are two types of questions: comparing cities (what time is it there right now?) and flight calculations (what time do I land?). Both use the same steps.

1
Write down both UTC offsets. You need to know where each city sits on the number line.
2
Find the difference. Subtract the smaller offset from the larger: difference = bigger offset − smaller offset
3
Add or subtract. Going east? Add the difference. Going west? Subtract the difference. Use the original time as your starting point.
4
For flight times: Add the flight duration before converting to local time. Convert to UTC first, add flight time, then convert to destination time.
⚠️ Daylight Saving Trap: In exam questions, the time zone offset will usually be stated in the question. Always use the offset you're given, don't assume Sydney is always UTC+10, because in summer it becomes UTC+11 (AEDT). Brisbane stays at UTC+10 all year.
4. Worked Examples

Example A · Comparing Cities

It is 18:00 in Brisbane (UTC+10). What time is it in London (UTC+0)?

Step 1: UTC offsets, Brisbane +10, London +0
Step 2: Difference = 10 − 0 = 10 hours
Step 3: London is west of Brisbane, so subtract: 18:00 − 10 = 08:00
✅ It is 08:00 in London when it's 18:00 in Brisbane.

Example B · Flight Arrival Time

A flight departs Brisbane (UTC+10) at 14:00. The flight is 9 hours. What is the local arrival time in Tokyo (UTC+9)?

Step 1: Convert departure to UTC. Brisbane is UTC+10, so: 14:00 − 10 = 04:00 UTC
Step 2: Add flight duration: 04:00 + 9 hours = 13:00 UTC
Step 3: Convert to Tokyo local time (UTC+9): 13:00 + 9 = 22:00
✅ The plane lands at 22:00 Tokyo time.

Example C · Reading it Backwards

It is 07:00 in New York (UTC−5). What time is it in Brisbane (UTC+10)?

Step 1: UTC offsets, New York −5, Brisbane +10
Step 2: Difference = 10 − (−5) = 15 hours
Step 3: Brisbane is east of New York, so add: 07:00 + 15 = 22:00
✅ It is 22:00 in Brisbane when it's 07:00 in New York.

Practice Questions

Q1  It is 10:00 in London (UTC+0). What time is it in Tokyo (UTC+9)? Tap to reveal
19:00 Tokyo time.
Tokyo is east of London: 10:00 + 9 = 19:00. Tokyo is 9 hours ahead.
Q2  A flight departs London (UTC+0) at 06:00 and takes 6 hours. It lands in Dubai (UTC+4). What is the local arrival time in Dubai? Tap to reveal
16:00 Dubai time.
Departure: 06:00 UTC (London = UTC+0, so no conversion needed).
+ 6 hours flight = 12:00 UTC.
Convert to Dubai (UTC+4): 12:00 + 4 = 16:00.
Q3  It is 07:00 in New York (UTC−5). What time is it in Brisbane (UTC+10)? Tap to reveal
22:00 in Brisbane.
Difference: 10 − (−5) = 15 hours. Brisbane is east, so add: 07:00 + 15 = 22:00.
Q4  Sydney is on AEDT (UTC+11) during summer. Perth is UTC+8. If it's 20:00 in Sydney, what time is it in Perth? Tap to reveal
17:00 in Perth.
Perth is west of Sydney. Difference: 11 − 8 = 3 hours. Subtract: 20:00 − 3 = 17:00.
Even though both are in Australia, daylight saving makes the gap 3 hours in summer.
Q5  A flight departs Brisbane (UTC+10) at 14:00 and lands in Los Angeles (UTC−8) after 13 hours. What local time does it arrive in LA? Tap to reveal
09:00 LA time.
Step 1 · convert departure to UTC: 14:00 − 10 = 04:00 UTC.
Step 2 · add flight duration: 04:00 + 13 = 17:00 UTC.
Step 3 · convert to LA (UTC−8): 17:00 − 8 = 09:00.

Note: LA is 18 hours behind Brisbane. Even though you flew for 13 hours, you "arrive" in LA's morning, the clocks don't match the flight time because you crossed many time zones heading east-to-west across the Pacific.
✈️ Escape Room
The World Clock
Josh is tracking six international flights for his school trip. Every clock is wrong and the departure board is frozen. Solve the time zone challenges before the gates close.
Start Escape Room →