24-hour time explained for parents (Australia)

Picture the school camp itinerary stuck on the fridge: bus departs 17:45. Your Year 5 child reads it, frowns, and announces the bus leaves at 7:45. That's a very common slip. They spotted the 7, knocked off the 1 and moved on. The real answer is 5:45 pm, two hours earlier, and on camp day that difference matters.

24-hour time looks like a whole new system, but it's only a different way of numbering the hours your child already knows. Once two small ideas click — after midday, keep counting past 12 and always use four digits — most of the confusion fades.

Below: converting both ways, the tricky midnight and midday cases, timetable problems and easy home practice. If reading a clock face is still shaky, the guide on digital and analogue time is the better place to begin.

What 24-hour time actually is

A 12-hour clock runs from 12 to 12 twice a day and leans on am and pm to tell morning from evening. A 24-hour clock simply keeps counting. The day starts at 00:00 (midnight), reaches 12:00 at midday, and carries on through 13:00, 14:00 and so on until 23:59, one minute before the next midnight.

Because each hour of the day has its own number, there's no need for am or pm. The time 08:00 can only mean morning; 20:00 can only mean evening.

Two conventions help children read it:

• Always four digits. Hours take the first two places and minutes the last two, so 7:05 in the morning becomes 07:05. That leading zero is a placeholder, much like the zero your child met when learning place value.
• The colon is optional. You'll see 17:45, 1745 and occasionally 17.45. They all mean the same moment.

Where Australian kids meet it

Plenty of children see 24-hour times every week without noticing: train, tram and bus timetables, flight bookings, phones set to a 24-hour display, oven and car dashboard clocks, and school camp itineraries.

Hospitals and emergency services use it too, because a mix-up between 7 am and 7 pm could be serious. That's a good "why should I care?" answer for a sceptical ten-year-old.

Mornings: nearly the same

From midnight to midday, the hour number doesn't change. You just write it with two digits and drop the am.

• 6:30 am → 06:30
• 9:15 am → 09:15
• 11:40 am → 11:40

The only snag is remembering the leading zero for hours below ten.

Afternoons and evenings: add 12

From 1 pm onward, add 12 to the hour and leave the minutes alone.

• 1:20 pm → 1 + 12 = 13:20
• 3:15 pm → 3 + 12 = 15:15
• 7:40 pm → 7 + 12 = 19:40
• 11:05 pm → 11 + 12 = 23:05

Why 12? At 1 pm, thirteen hours have passed since midnight, and the 24-hour clock just reports that full count. Adding 12 to a single-digit hour is a fact most Year 5 children know, so this is really an addition job in disguise.

Going back: take away 12

To turn an afternoon or evening 24-hour time into 12-hour time, subtract 12 from the hour and add pm.

• 14:30 → 14 − 12 = 2, so 2:30 pm
• 17:45 → 17 − 12 = 5, so 5:45 pm
• 20:10 → 20 − 12 = 8, so 8:10 pm
• 22:55 → 22 − 12 = 10, so 10:55 pm

The camp-bus error from the start comes from taking away 10 instead of 12. A quick shortcut for hours 13 to 19: take 2 off the last digit. So 16 becomes 4 pm and 19 becomes 7 pm. For 20 to 23, plain subtraction of 12 is safer.

The tricky bits: midnight and midday

The hours around 12 cause the most arguments, even among adults.

12-hour time	24-hour time	Notes
12:00 midnight (12 am)	00:00	Start of a new day
12:30 am	00:30	Half an hour after midnight
6:30 am	06:30	Add a leading zero
12:00 midday (12 pm)	12:00	No change at all
12:45 pm	12:45	Still no change
9:20 pm	21:20	Add 12 to the hour

The awkward truth is that "12 am" and "12 pm" confuse lots of people, which is exactly why 24-hour time exists. In everyday talk, saying "midnight" or "midday" avoids the problem altogether.

Some timetables also show 24:00, meaning the very end of a day — the same instant as 00:00 the next day.

How people say it out loud

Australians usually read 24-hour times as two pairs: 14:30 is "fourteen thirty", 19:05 is "nineteen oh five", 17:00 is "seventeen hundred" and 07:15 is "oh seven fifteen".

Saying the time aloud and then translating it ("nineteen oh five — that's five past seven at night") is a great checking habit.

Working with timetables

This is where 24-hour time earns its keep, and where the curriculum takes it next. A few home-style problems (answers in bold):

How long is the train trip? A train leaves at 16:48 and arrives at 18:05. Count on: 16:48 to 17:00 is 12 minutes, 17:00 to 18:00 is one hour, 18:00 to 18:05 is 5 minutes. Total: 1 hour 17 minutes. Jumping to the next whole hour first is exactly the strategy in elapsed time, and sketching the jumps on an empty number line keeps it tidy.

When does the movie finish? A film starts at 19:15 and runs for 1 hour 50 minutes. 19:15 plus 1 hour is 20:15; plus 45 minutes is 21:00; plus the last 5 minutes is 21:05, or 9:05 pm.

Which bus do we catch? Buses leave at 08:12, 08:37 and 09:02, and the ride takes 25 minutes. To arrive by 9:05 am, the latest bus that works is the 08:37, arriving at 09:02; the 09:02 bus would arrive at 09:27, too late.

How long did I sleep? Lights out at 21:30, awake at 06:45. From 21:30 to midnight is 2 hours 30 minutes, then midnight to 06:45 is 6 hours 45 minutes. Together: 9 hours 15 minutes. Crossing midnight is a stretch for Year 5 and a good challenge for keen Year 6s.

One trap with timetables: you can't subtract times like ordinary numbers. 18:05 − 16:48 done as 1805 − 1648 gives 157, which isn't 1 hour 57 minutes or anything else useful, because an hour holds 60 minutes, not 100. Counting on in chunks avoids it. Story-style versions of these problems sit well alongside word problems.

Linking it to the clock face

On an analogue clock the hour hand goes around twice a day, so 3 o'clock and 15:00 point to the same spot. Some classroom clocks print the numbers 13 to 24 in a small inner ring, which makes the link visible. Year 5 classes often match the same time shown digitally, in 24-hour form and on a clock face, then set an analogue watch from a digital alarm clock.

When schools teach it

In the Australian Curriculum: Mathematics, now at version 9, 24-hour time arrives in Year 5, where students compare the 12- and 24-hour systems and solve practical problems that involve converting between them, such as using a flight schedule to plan a trip.

The groundwork comes earlier. Year 3 students read time to the nearest minute on analogue and digital clocks, and Year 4 students solve duration problems that involve am and pm and convert between units of time (converting units covers hours, minutes and seconds). In Year 6 the focus moves to interpreting timetables and itineraries to plan activities and work out how long journeys take. Victoria's Curriculum 2.0 follows the same pattern, and schools choose their own order within each year. The curriculum levels explainer has more on how these year bands work.

How time skills build, Prep to Year 6

Prep–Year 2: sequencing parts of the day, days of the week and months, then reading o'clock, half past and quarter times on a clock face.

Year 3: reading time to the minute and knowing there are 60 minutes in an hour and 24 hours in a day. Overview: Year 3.

Year 4: am and pm, simple durations, converting hours to minutes. Counting in fives, covered in skip counting, does a lot of the work here. Overview: Year 4.

Year 5: 24-hour time and converting both ways, often with timetables. Overview: Year 5.

Year 6: reading full timetables and itineraries, planning trips and finding journey times. Overview: Year 6.

Being a little ahead of or behind these markers is perfectly normal.

Questions that help at home

Short chats beat worksheets. Try:

• "Is that time in the morning or after midday? How do you know?"
• "What would that look like on our kitchen clock?"
• "If it's 16:00, how many hours until dinner at 18:30?"
• "Why does 07:00 have a zero at the front?"
• "Say it in 24-hour time, then say it the normal way. Do they match?"

If practice turns tense, stop and try another day (homework without tears has ideas for keeping the peace).

Five quick games

1. Switch the phone. For one week, set a family tablet or phone to 24-hour display. Each time your child checks it, they say the 12-hour version.
2. Timetable detective. Print a local bus, tram or train timetable. Pick a departure and ask your child to find when it reaches a certain stop and how long the trip takes.
3. Snap pairs. Make cards with matching times (15:20 and 3:20 pm, 08:05 and 8:05 am). Lay them face down and play memory.
4. Plan the day. Let your child write tomorrow's family plan in 24-hour time: breakfast 07:30, sport 16:15, bed 20:00.
5. Catch me out. Say a deliberately wrong conversion, such as "18:00 is 8 pm", and let your child correct you and explain why.

Common mistakes and how to fix them

Taking away 10 instead of 12. 17:45 read as 7:45 pm. Remind them that the hours past midday start at 13 for 1 pm, so 17 is five hours on.

Adding 12 to morning times. Turning 9:00 am into 21:00. Ask "Is it before or after lunch?" before converting.

Muddling midnight and midday. Writing 12:00 for midnight or 00:00 for lunchtime. Keep the table above handy, or use the words "midnight" and "midday".

Treating times as ordinary numbers. 10:20 minus 09:50 done as 1020 − 950 gives 70 minutes; the real gap is 30. Count on to the next whole hour instead.

Forgetting there are 60 minutes in an hour. Adding 45 minutes to 10:30 and getting 10:75. A quick "what comes after 59 minutes?" usually sorts it.

When to get extra help

If your child still can't read an ordinary clock face by the end of Year 4, or 24-hour conversions remain a mystery after a term of calm practice, have a chat with the classroom teacher about how time is being taught and practised.

If the worry is wider than clocks, our guides on whether your child is behind in maths, nerves around maths and signs worth acting on are good next steps. Nothing here can assess your particular child; if difficulty with time persists, raise it with the school or a suitably qualified professional.

FAQ

How do you convert 24-hour time to 12-hour time?

If the hour is 13 or more, subtract 12 and add pm (18:20 is 6:20 pm). If it's between 01 and 11, keep the number and add am. 00 means the midnight hour and 12 means the midday hour.

Is midnight 00:00 or 24:00?

Usually 00:00, the start of a new day. Some timetables use 24:00 to mean the end of a day. Both point to the same instant.

Why does 24-hour time have a zero at the start?

So every time has four digits: two for hours, two for minutes. 07:15 can't be mistaken for anything else.

What year do Australian kids learn 24-hour time?

In the Australian Curriculum (version 9) it's a Year 5 skill, built on reading clocks in Year 3 and am/pm durations in Year 4. Schools vary in exact timing.

A small mission for this week

Next time you're heading somewhere by public transport or plane, hand the timetable or boarding pass to your child. Ask them to tell you, in ordinary words, when you leave and when you'll get there. A real trip with real stakes teaches 24-hour time far better than a worksheet.

Wondering how your child is going with numbers more generally? Ziado's free check is a roughly ten-minute adaptive diagnostic you can do at home, and you'll see a portion of the results straight away without creating an account or entering card details. Signing up unlocks the full placement. It doesn't test time-telling on its own, it isn't NAPLAN preparation, and it can't diagnose a learning difficulty or medical condition. The Ziado maths page outlines how ongoing practice works, you can try either the Individual or the Family plan free for 14 days, and pricing has the details.