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 calculating — how 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 |
What to write in your book
- 24-hr time: midnight = 0000, noon = 1200. Four digits always — leading zero for single-digit hours (e.g. 0915).
- am → 24-hr: same digits. pm → 24-hr: add 12 to hour. (Exception: 12 pm = 1200, not 2400.)
- 24-hr → 12-hr: if hour ≥ 13, subtract 12 and write pm. If 1200, write 12 pm (noon). If 0000, write midnight.
- Time conversion: $1 \text{ h} = 60 \text{ min}$; $1 \text{ h} = 3600 \text{ s}$. Decimal hours: e.g. 2 h 35 min $= 2 + \frac{35}{60} \approx 2.583$ h.
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 |
What to write in your book
- Count-up method: 1) convert to 24-hr, 2) count whole hours, 3) count remaining minutes, 4) add together.
- Crossing midnight: add 2400 to finish time, then subtract. Or count: start → 0000 + 0000 → finish.
- Timetable reading: each column = one service. Find the row for your boarding stop and check each column for the next available time.
- Decimal hours: minutes ÷ 60. e.g. 2 h 35 min = $2 + \frac{35}{60} \approx 2.58$ h.
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
What to write in your book
- 12 pm = 1200; 12 am = 0000. Memorise these two exceptions.
- For any elapsed time, use the count-up method to avoid borrowing errors.
- If finish < start in 24-hr: add 2400 to finish time, then subtract.
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 confidence — that 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.
⚔ Enter the arenaClimb platforms by answering timetable and elapsed time questions. Pool: lesson 20.
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