(Topic 6 Task 6) Time Conversion Guide

Overview

This lecture explains how to convert between AM/PM (12-hour) and 24-hour clock systems, including key rules, examples, and areas where confusion can occur.

Basics of Time Representation

• Time is generally shown as Hours:Minutes (e.g., 10:25 means 10 hours and 25 minutes).
• There are 24 hours in a day and 60 minutes in each hour.
• Two main ways to show time: 24-hour clock and AM/PM (12-hour clock).

AM/PM (12-Hour Clock) System

• AM represents "Ante Meridiem," which means before midday, from midnight to noon.
• PM stands for "Post Meridiem," meaning after midday, from noon to midnight.
• In 24-hour format, AM covers 00:00 to 11:59, PM covers 12:00 to 23:59.

Converting AM/PM to 24-Hour Clock

• For 12:00 AM to 12:59 AM, subtract 12 (e.g., 12:35 AM = 00:35).
• For 1:00 AM to 12:59 PM, time stays the same in 24-hour format (e.g., 11:20 AM = 11:20).
• For 1:00 PM to 11:59 PM, add 12 to the hour (e.g., 4:45 PM = 16:45).

Converting 24-Hour Clock to AM/PM

• For 00:00 to 00:59, add 12 hours and use AM (e.g., 00:10 = 12:10 AM).
• From 01:00 to 11:59, use the same time and add AM (e.g., 09:10 = 9:10 AM).
• From 12:00 to 12:59, use the same time and add PM (e.g., 12:10 = 12:10 PM).
• For 13:00 to 23:59, subtract 12 and add PM (e.g., 14:55 = 2:55 PM).

Midnight and Noon

• "12 AM" means midnight, "12 PM" means noon; using "midnight" and "noon" is clearer.
• Midnight can refer to either the start or end of a day, so using 11:59 PM or 12:01 AM (or 23:59/00:01) avoids confusion.

Key Terms & Definitions

• AM (Ante Meridiem) — Latin for "before midday"; midnight to noon.
• PM (Post Meridiem) — Latin for "after midday"; noon to midnight.
• 24-Hour Clock — Shows hours and minutes since midnight, ranging from 00:00 to 23:59.
• Midnight — 12:00 AM or 00:00, marking the start of a new day.
• Noon — 12:00 PM or 12:00, marks the middle of the day.

Action Items / Next Steps

• Practice converting given times between AM/PM and 24-hour clock formats.
• Avoid using just "midnight"; specify 11:59 PM or 12:01 AM for clarity in time-sensitive situations.