Duration, 12/24-Hour Time and Time Zones — AC9M8M04

• Convert accurately between 12-hour and 24-hour time.
• Calculate duration across noon, midnight and date changes.
• Use UTC offsets to compare local times across zones.
• Interpret travel schedules and meeting times while accounting for daylight saving where specified.

Recall hours/minutes, am/pm notation, addition/subtraction across 60 minutes and 24 hours, signed-number offsets and reading timetables.

A clock time tells when an event occurs; a duration measures the interval between two moments. Displayed local times cannot usually be subtracted directly when locations have different UTC offsets.

A reliable method is: write each location’s offset, convert both moments to UTC (or another shared reference), compare them there, then convert back if the answer requires a local time. Crossing midnight may change the calendar date.

Preserve the AC9 elaborations: using digital tools to compare Perth with places such as Suva or Toronto, planning recurring virtual meetings across Australian jurisdictions with daylight-saving complications, and creating international travel itineraries across Asian time zones.

• Subtracting local times directly. Convert to one common zone first.
• Treating 12:00 am as noon. 12:00 am is midnight; 12:00 pm is noon.
• Ignoring the date. Time-zone conversion or travel can cross into the previous/next day.
• Assuming an Australian zone’s offset never changes. Daylight saving may change the offset in some jurisdictions and dates.

1. Convert 6:48 am, 12:05 pm and 9:17 pm to 24-hour time.
2. Find the duration from 18:55 to 22:30.
3. Find the duration from 23:40 to 02:15 next day.
4. Convert 10:00 at UTC+8 to UTC+12.

1. Convert 00:35, 13:10 and 21:45 to 12-hour notation.
2. A webinar begins 16:30 UTC. Find local time at UTC+10.
3. When it is 08:15 at UTC−5, what time is it at UTC+1?
4. A journey starts at 20:25 and lasts 7 h 50 min. Find the finish time/date relation.
5. Explain why UTC offsets behave like signed numbers.
6. Design a meeting time that falls between 09:00 and 17:00 in two given zones.
7. Identify one daylight-saving detail that must be checked before planning a recurring meeting.

A company has staff in Perth, Sydney and Toronto and wants one weekly 60-minute meeting during each office’s 08:00–18:00 window. Explain how you would test whether a feasible time exists on a given date, including which offsets must be checked and why the answer can change during the year.

1. Why use 24-hour time? It removes am/pm ambiguity and is useful for schedules.
2. Why convert to UTC? It provides one common reference for different zones.
3. What can happen when an offset pushes time past 24:00? The calendar date changes.
4. Why can a recurring meeting shift seasonally? Some locations change UTC offset for daylight saving while others do not.

1. At 15:20 in Perth (UTC+8), find the time in a location at UTC−4.
   Convert Perth to UTC first, then apply −4 and state any date change.
2. A flight leaves a UTC+10 city at 21:35 and arrives at a UTC+1 city at 07:05 next local day. Find elapsed flight time.
   Convert both moments to UTC before subtracting.
3. Explain why a 09:00 Sydney meeting may not represent the same UTC time in January and July.
   Discuss daylight-saving offset changes where applicable.

• I distinguish clock time and duration.
• I use 12/24-hour notation accurately.
• I convert via a common UTC reference.
• I track date/daylight-saving effects.

Exit ticket: Why is 03:00−22:00 not simply a negative 19-hour duration?

Australian Curriculum v9.0 — AC9M8M04: solve problems involving duration, including using 12- and 24-hour time across multiple time zones.

Victorian Curriculum F–10 Version 2.0 — Level 8, VC2M8M04: Exact.

NSW Mathematics K–10 Syllabus (2022) — Stage 4, MA4-RAT-C-01; MAO-WM-01: Supporting. NSW Stage 4 has no clean one-outcome equivalent for the full national time-zone descriptor; rate/distance-time and Working mathematically support elapsed-time reasoning without pretending exact equivalence.

• AC9M8M05 — rates and unit rates
• AC9M8M07 — modelling ratios and rates

• Australian Curriculum v9.0
• Victorian Curriculum F–10 Version 2.0 Mathematics
• NSW Mathematics K–10 Syllabus (2022)

Curriculum equivalents for Solve problems involving duration, including using 12- and 24-hour time...

Mapped skill: solve problems involving duration, including using 12- and 24-hour time across multiple time zones

These references identify matching or closely related learning. Curriculum sequence, terminology and depth vary, so teachers should use the mapped skill and lesson difficulty to confirm suitability.

Australian Curriculum v9.0 is the canonical source for this SkillrHub lesson. Victoria and NSW entries name the closest published state codes or outcomes; international entries are planning references rather than claims of identical curricula.