Source: https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-1-2-changing-the-12-hour-clock-to-the-24-hour-clock

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# Changing the 12-Hour Clock to the 24-Hour Clock

11+ Maths, topic 3.1.2

## Changing from the 12-Hour to the 24-Hour Clock

You may be asked to convert a time from the 12-hour clock to the 24-hour clock.

### Example problem

![Example problem](https://image-v2.cdn.app.senecalearning.com/2019-04/76b7824c-2963-4f64-9aae-6ccc845f3344/clock%20(8).png)

- What is 6.30pm in the 24-hour clock?

### Change to the 24-hour clock

![Change to the 24-hour clock](https://image-v2.cdn.app.senecalearning.com/2019-04/76b7824c-2963-4f64-9aae-6ccc845f3344/clock%20(8).png)

- 6.30pm is in the afternoon, so we need to add 12 to the first number to get the time in the 24-hour clock.
 - 6 + 12 = 18
    - So 6.30pm is 18.30 in the 24-hour clock.

### Example problem

![Example problem](https://image-v2.cdn.app.senecalearning.com/2019-04/319537d8-bb66-42dd-be06-6269078752b4/clock%20(11).png)

- What is 8.45am in the 24-hour clock?

### Change to the 24-hour clock

![Change to the 24-hour clock](https://image-v2.cdn.app.senecalearning.com/2019-04/319537d8-bb66-42dd-be06-6269078752b4/clock%20(11).png)

- 8.45am is in the morning, so the hourly time stays the same in the 24-hour clock.
 - 8.45am is 08.45 in the 24-hour clock.

### What about 12am?

![What about 12am?](https://image-v2.cdn.app.senecalearning.com/2019-06/197ad1ec-b681-492d-86fa-c837f1a08815/midnight-12-.png)

- 12am is written as 00.00 in the 24-hour clock.
 - So 12.59am would be 00.59 in the 24-hour clock.

## Test yourself on Changing the 12-Hour Clock to the 24-Hour Clock

- What's 3pm in the 24-hour clock?
- What's 1.04am in the 24-hour clock?
- Your train is scheduled to leave at 3.15pm.What time is this in the 24-hour clock?
- Sheila is going horse riding at 8.30am.What time is this in the 24-hour clock?

[Practise this topic for free](https://app.senecalearning.com/classroom/course/f4a9de91-3dcc-4e19-b180-1286357dded5/section/a7cede25-5643-467f-bcdd-cf52a2db2fdf/session)

- Previous topic: [3.1.1 Difference Between 12-Hour & 24-Hour Clocks](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-1-1-difference-between-12-hour-and-24-hour-clocks.md)
- Next topic: [3.1.3 Changing the 24-hour Clock to the 12-Hour Clock](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-1-3-changing-the-24-hour-clock-to-the-12-hour-clock.md)

## 11+ Maths contents

### 1 Angles
- 1.1 7 Facts About Angles
  - [1.1.1 Facts About Angles](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/1-1-1-facts-about-angles.md)
  - [1.1.2 More Facts About Angles](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/1-1-2-more-facts-about-angles.md)
- 1.2 Identify the Angle
  - [1.2.1 Identify the Angle](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/1-2-1-identify-the-angle.md)
- 1.3 Angles on a Straight Line
  - [1.3.1 Angles on a Straight Line](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/1-3-1-angles-on-a-straight-line.md)
  - [1.3.2 Angles on a Straight Line - Practice Questions](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/1-3-2-angles-on-a-straight-line-practice-questions.md)
- 1.4 Angles in a Circle
  - [1.4.1 Angles in a Circle](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/1-4-1-angles-in-a-circle.md)
- 1.5 Angles in Triangles
  - [1.5.1 Angles in a Triangle](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/1-5-1-angles-in-a-triangle.md)

### 2 Fractions
- 2.1 Simplifying Fractions
  - [2.1.1 Simplifying Fractions](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/2-1-1-simplifying-fractions.md)
  - [2.1.2 Identifying Equivalent Fractions](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/2-1-2-identifying-equivalent-fractions.md)
- 2.2 Improper Fractions & Mixed Numbers
  - [2.2.1 Improper Fractions & Mixed Numbers](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/2-2-1-improper-fractions-and-mixed-numbers.md)
  - [2.2.2 Converting Mixed Numbers to Improper Fractions](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/2-2-2-converting-mixed-numbers-to-improper-fractions.md)
  - [2.2.3 Converting Improper Fractions to Mixed Numbers](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/2-2-3-converting-improper-fractions-to-mixed-numbers.md)
- 2.3 Fractions of Numbers
  - [2.3.1 Fractions of Numbers](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/2-3-1-fractions-of-numbers.md)
- 2.4 Expressing Shaded Areas as Fractions
  - [2.4.1 Expressing Shaded Areas as Fractions](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/2-4-1-expressing-shaded-areas-as-fractions.md)

### 3 Time
- 3.1 12-Hour & 24-Hour Clocks
  - [3.1.1 Difference Between 12-Hour & 24-Hour Clocks](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-1-1-difference-between-12-hour-and-24-hour-clocks.md)
  - [3.1.2 Changing the 12-Hour Clock to the 24-Hour Clock](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-1-2-changing-the-12-hour-clock-to-the-24-hour-clock.md)
  - [3.1.3 Changing the 24-hour Clock to the 12-Hour Clock](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-1-3-changing-the-24-hour-clock-to-the-12-hour-clock.md)
- 3.2 Time-Related Problems
  - [3.2.1 Time-Related Problems](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-2-1-time-related-problems.md)
  - [3.2.2 Timetable & Schedule Problems](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/3-2-2-timetable-and-schedule-problems.md)

### 4 Prime Numbers
- 4.1 Prime Numbers
  - [4.1.1 Prime Numbers](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/4-1-1-prime-numbers.md)

### 5 Probability
- 5.1 Probability
  - [5.1.1 Probability Scale](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/5-1-1-probability-scale.md)
  - [5.1.2 Probability Fractions](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/5-1-2-probability-fractions.md)
  - [5.1.3 Experimental Probability](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/5-1-3-experimental-probability.md)

### 6 Ratio
- 6.1 Ratios
  - [6.1.1 Ratios](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/6-1-1-ratios.md)

### 7 Sequences
- 7.1 Constant Sequences
  - [7.1.1 Constant Increase Sequences](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-1-1-constant-increase-sequences.md)
  - [7.1.2 Constant Decrease Sequences](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-1-2-constant-decrease-sequences.md)
- 7.2 Doubling & Halving Sequences
  - [7.2.1 Doubling Sequences](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-2-1-doubling-sequences.md)
  - [7.2.2 Halving Sequences](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-2-2-halving-sequences.md)
- 7.3 Alternating Patterns & Two-Step Sequences
  - [7.3.1 Alternating Pattern Sequences](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-3-1-alternating-pattern-sequences.md)
- 7.4 Two-Step Patterns
  - [7.4.1 Two-Step Patterns](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-4-1-two-step-patterns.md)
- 7.5 The nth Term
  - [7.5.1 Find the nth Term](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-5-1-find-the-nth-term.md)
  - [7.5.2 Using the nth Term](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/7-5-2-using-the-nth-term.md)

### 8 Area & Perimeter
- 8.1 Perimeter of a Quadrilateral
  - [8.1.1 Finding the Perimeter of a Quadrilateral](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/8-1-1-finding-the-perimeter-of-a-quadrilateral.md)
  - [8.1.2 Finding the Missing Length](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/8-1-2-finding-the-missing-length.md)
- 8.2 Area of a Quadrilateral
  - [8.2.1 Finding the Area of a Quadrilateral](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/8-2-1-finding-the-area-of-a-quadrilateral.md)
  - [8.2.2 Finding the Missing Side of a Rectangle](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/8-2-2-finding-the-missing-side-of-a-rectangle.md)
  - [8.2.3 Finding the Missing Side of a Square](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/8-2-3-finding-the-missing-side-of-a-square.md)
  - [8.2.4 Finding the Area of Irregular Shapes](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/8-2-4-finding-the-area-of-irregular-shapes.md)
- 8.3 Area of a Triangle
  - [8.3.1 Finding the Area of a Triangle](https://senecalearning.com/en-gb/revision-notes/11/maths/11-maths/8-3-1-finding-the-area-of-a-triangle.md)