The 12-hour clock uses am (midnight to noon) and pm (noon to midnight). The 24-hour clock runs from 0000 to 2359 with no am/pm needed. To convert a pm time to 24-hour format, add 12 to the hour. For am times, keep the hours the same (padding with a zero if needed). Special cases: midnight = 00:00, noon = 12:00.
12-Hour
24-Hour
Notes
12:00 am (midnight)
00:00
Start of the day
6:00 am
06:00
Same hour, add leading zero
12:00 pm (noon)
12:00
Special case — stays as 12
6:00 pm
18:00
6 + 12 = 18
11:59 pm
23:59
11 + 12 = 23
Tip: For am times (except midnight), the 24-hour time is the same — just use a leading zero: 9:15 am = 09:15. For pm times, add 12 to the hour: 9:15 pm = 21:15.
✔ Quick Check ttsch1 — 12-hour and 24-hour clock
Question 1 of 10
Reading Timetables
Timetables are grids: rows are stops or stations, columns are different services (different buses or trains). Reading across a row gives the departure times for that stop across different services. Reading down a column follows a single service's journey. A dash (—) means the service does not stop there.
Example — Using the timetable above
Question
What time does Service A arrive at Stop C?
Answer
Find the column for Service A and read down to the row for Stop C: 09:40
Question
Which is the fastest service from Town A to Town D?
Answer
Service B: departs 10:15, arrives 11:10 = 55 minutes. Service A = 65 minutes, Service C = 65 minutes. Service B is fastest.
Common error: Switching columns mid-journey. Each column is one service — stay in the same column to follow a single bus or train.
✔ Quick Check ttsch2 — Reading timetables
Question 1 of 10
Calculating with Timetables
To find a journey duration, count up from the departure time to the arrival time in stages — do not subtract times as if they were ordinary numbers.
Count up in stages: minutes to the hour → whole hours → remaining minutes
Example (a) — Find journey duration
Problem
Train leaves 08:35, arrives 11:10. How long is the journey?
Stage 1
08:35 → 09:00 = 25 minutes
Stage 2
09:00 → 11:00 = 2 hours
Stage 3
11:00 → 11:10 = 10 minutes
Total
2 hours 35 minutes
Example (b) — Find departure time
Problem
Journey takes 2h 45min, arrives 16:20. What time did it leave?
Step 1
Count back 45 minutes from 16:20: 16:20 → 15:35
Step 2
Count back 2 hours from 15:35: 13:35
Key rule: Never subtract times like ordinary numbers. 11:10 − 08:35 does NOT equal 2:75. Always count up (or back) in stages.
✔ Quick Check ttsch3 — Calculating with timetables
Question 1 of 10
Practice: Mini Timetable Practice
Use the timetable below to answer the questions. Type your answers and click Check.
Stop
Service 1
Service 2
Service 3
Stop A
09:05
10:20
13:45
Stop B
09:38
10:53
14:18
Stop C
10:00
11:15
14:40
Q1. What time does the 10:20 from Stop A arrive at Stop C? (write as HH:MM)
Q2. How many minutes does Service 1 take from Stop A to Stop C? (just the number)
Q3. You need to arrive at Stop B by 14:00. What is the latest service you can catch from Stop A? (write the departure time)
Q4. What time does Service 3 depart from Stop A?
Q5. How long does Service 2 take from Stop A to Stop B? (minutes)
Q6. What time does Service 1 arrive at Stop B?
Q7. How many minutes does Service 3 take from Stop B to Stop C?
Q8. What time does Service 3 arrive at Stop C?
Q9. How many minutes does Service 1 take from Stop B to Stop C?
Q10. You need to arrive at Stop C by 12:00. What is the latest departure time from Stop B?
⚠ Things to Watch Out For
Confusing am and pm: 12:00 am is midnight (start of the day). 12:00 pm is noon (midday). These are the two most commonly confused times.
Subtracting times incorrectly: You cannot subtract 09:47 from 13:22 like regular numbers (13:22 − 09:47 ≠ 4:75). Count up in stages instead.
Reading the wrong column: In a timetable, each column is a separate service. Make sure you stay in the same column for a single journey.
Forgetting that 24-hour clock has no colon in some formats: 0947 and 09:47 mean the same thing — the colon is sometimes omitted on timetables.
Missing services shown by a dash: A dash (—) in a timetable means the bus or train does not stop there — it is not a zero or a blank. Don't read it as a time.