Timetables and Elapsed Time
Reading a timetable and calculating how long a journey takes sounds simple, until the train crosses midnight or the flight has a 2-hour layover. Master the structured method and nothing trips you up.
Practise this lesson
Three printable worksheets that build from foundations to mastery, or build your own from any module’s questions.
A train departs Sydney at 11:48 pm and arrives in Newcastle at 1:23 am the next day. Your friend says the journey is "1 hour and 35 minutes."
Without calculatinghow would you check this? Is there a reliable method that doesn't rely on mental arithmetic, one that works even when the clock crosses midnight?
Come back to this at the end of the lesson.
Time calculations hinge on two skills: converting between 12-hr and 24-hr time, and calculating elapsed time reliably, even across midnight.
24-hour time uses four digits (HHMM) from 0000 to 2359. There is no am/pm, midnight = 0000, noon = 1200.
To convert pm to 24-hr: add 12 to the hour. (Exception: 12 pm stays as 1200; 12 am = 0000.)
Key facts
- How to convert between 12-hour and 24-hour time
- Midnight = 0000 (or 2400), Noon = 1200
- How to calculate elapsed time by subtracting start from finish
- How to handle elapsed time that crosses midnight
Concepts
- Why 24-hour time eliminates the am/pm ambiguity
- Why you can't just subtract when the finish time crosses midnight (add 24 h first)
- How timetable columns relate to different services/vehicles
Skills
- Read train, bus, or flight timetables and extract relevant information
- Calculate journey times including layovers and connections
- Calculate elapsed time across midnight
- Convert between hours:minutes and decimal hours
The 24-hour clock avoids all ambiguity: there is no need to specify am or pm. It is used universally in transport timetables, the military, and aviation.
| 12-hour time | 24-hour time | Rule |
|---|---|---|
| 12:00 midnight | 0000 | Start of day |
| 12:30 am | 0030 | am: write directly (add leading zero if needed) |
| 9:15 am | 0915 | am: same digits |
| 12:00 noon | 1200 | Noon stays as 1200 |
| 1:00 pm | 1300 | pm: add 12 to the hour (1 + 12 = 13) |
| 7:45 pm | 1945 | pm: 7 + 12 = 19 → 1945 |
| 11:59 pm | 2359 | pm: 11 + 12 = 23 → 2359 |
24-hour clock: no am/pm. 0000 = midnight; 1200 = noon; 1800 = 6 pm. Converting 12-hour pm to 24-hour: add 12 (except 12 pm = 1200). Converting 24-hour ≥ 1300 to 12-hour: subtract 12 and add pm. Midnight = 0000 or 2400.
Pause, copy the 24-hour clock conversion rules: 12-hour pm → 24-hour: add 12 (except 12:00 pm = 1200); 24-hour ≥ 1300 → 12-hour: subtract 12 and add "pm"; midnight = 0000 (start of day) or 2400 (end of day), and note that 1200 is noon, not midnight into your book.
Did you get this? True or false: 12:30 pm in 24-hour time is written as 0030.
Worked examples · 3 in a row, reveal as you go
A bus departs at 10:47 am and arrives at 2:23 pm. How long does the journey take?
An overnight train departs at 11:48 pm and arrives at 6:15 am the next morning. Find the journey time.
Use the train timetable extract below.
(a) How long does Service A take from Central to Penrith?
(b) A passenger arrives at Parramatta at 8:40 am. Which is the next service they can catch, and when does it arrive in Penrith?
(c) How long must the passenger wait at Parramatta?
| Station | Service A | Service B | Service C |
|---|---|---|---|
| Central | 0743 | 0812 | 0857 |
| Strathfield | 0758 | 0827 | 0912 |
| Parramatta | 0814 | 0843 | 0929 |
| Blacktown | 0829 | 0858 | 0944 |
| Penrith | 0856 | 0925 | 1011 |
Quick check: A shift starts at 2230 and ends at 0115 the next day. What is the correct method for finding the elapsed time?
Common errors · the 3 traps that cost marks
Fill the gap: A night bus departs at 10:40 pm and arrives at 2:05 am. In 24-hour time, departure = and arrival = . Since arrival < departure, add 2400: adjusted arrival = . Elapsed time = 2605 − 2240 = .
Quick-fire practice · 5 questions
Convert to 24-hour time: (a) 7:20 am (b) 4:55 pm (c) 12:10 am (d) 12:30 pm
Convert to 12-hour time: (a) 0635 (b) 1410 (c) 0005 (d) 2258
Find the elapsed time from 0845 to 1327.
A night bus departs at 10:40 pm and arrives at 2:05 am. Find the journey time.
A shift starts at 2330 and ends at 0645 the next morning. How long is the shift?
Two truths, one lie: Three statements below are correct. Which one is the lie?
Odd one out: Three of these are valid elapsed-time scenarios. Which one requires a different technique?
Look back at what you wrote in the Think First section. Let's check: depart 11:48 pm = 2348; arrive 1:23 am = 0125. Count: 2348 → 0000 = 12 min; 0000 → 0125 = 1 h 25 min. Total = 1 h 37 min. Your friend said 1 h 35 min, only 2 minutes out, but the method matters for larger journeys.
Pick your answer, then rate your confidencethat tells the system what to drill next. Each retry pulls a fresh mix from the bank.
Q1. A student works a shift from 6:45 pm to 1:10 am.
(a) Write both times in 24-hour format. (1 mark)
(b) Calculate the length of the shift in hours and minutes. (2 marks)
Q2. Use the timetable from Worked Example 3 (Service A, B, C between Central and Penrith).
(a) How long does Service B take from Central to Penrith? (1 mark)
(b) A passenger arrives at Strathfield at 8:30 am. What is the earliest service they can catch, and when does it reach Penrith? (2 marks)
(c) How much longer does Service C take from Central to Penrith compared to Service A? (1 mark)
Q3. A flight from Sydney departs at 2150. It has a 1 hour 40 minute layover in Singapore. The second leg takes 6 hours 15 minutes and lands in London.
(a) The first leg (Sydney to Singapore) takes 8 hours 20 minutes. At what 24-hour time does the plane land in Singapore? (2 marks)
(b) At what 24-hour time does the plane depart Singapore? (1 mark)
(c) What is the total elapsed time from Sydney departure to London arrival? (1 mark)
📖 Comprehensive answers (click to reveal)
Drill 1: (a) 0720 (b) 1655 (c) 0010 (d) 1230
Drill 2: (a) 6:35 am (b) 2:10 pm (c) 12:05 am (d) 10:58 pm
Drill 3: $1327 - 0845$: count-up: 0845 + 4 h = 1245; 1245 → 1327 = 42 min; total = $\mathbf{4\text{ h }42\text{ min}}$
Drill 4: Depart 2240, arrive 0205; add 2400: $2605 - 2240$: 40 min to midnight (2240→2300=20, 2300→0000=60, 0000→0205=2h5); count: 2240→0000 = 80 min; 0000→0205 = 2h5; total = $\mathbf{3\text{ h }25\text{ min}}$
Drill 5: 2330→0000 = 30 min; 0000→0645 = 6h 45min; total = $\mathbf{7\text{ h }15\text{ min}}$
Q1 (3 marks): (a) 6:45 pm = 1845; 1:10 am = 0110 [1]. (b) 1845 to 0000 = 3 h 15 min; 0000 to 0110 = 1 h 10 min; total = 6 h 25 min [2].
Q2 (4 marks): (a) $0925 - 0812 = \mathbf{1\text{ h }13\text{ min}}$ [1]. (b) 8:30 am = 0830; Service B at Strathfield = 0827 (already gone); Service C at Strathfield = 0912 (next). Service C arrives Penrith at 1011 [2]. (c) Service A: 1 h 13 min; Service C: $1011-0857 = 1\text{ h }14\text{ min}$; difference = 1 min [1].
Q3 (4 marks): (a) $2150 + 8\text{h}\,20 = 2150 + 8\text{h} = 0550 + 20\text{min} = \mathbf{0610}$ (next day) [2]. (b) $0610 + 1\text{h}\,40 = \mathbf{0750}$ [1]. (c) Total = 8h20 + 1h40 + 6h15 = 16 h 15 min [1].
Five timed questions on timetables and elapsed time. Beat the boss to bank a tier, gold (90% + speed), silver (75%), or bronze (50%). Replays welcome.
Climb platforms by answering timetable and elapsed time questions. Pool: lesson 20.
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