Time Zones & Global Timekeeping
How the world coordinates time across 24 zones — and what the International Date Line does
Learning Objectives
- Explain the concept and purpose of time zones and how they affect global timekeeping
- Identify and name major time zones and their abbreviations
- Convert time between different time zones using simple calculations
- Understand the role of the International Date Line and how it affects calendar dates
Key Concept
When you travel east, you add hours. When you travel west, you subtract hours. If it's 3:00 PM UTC and you're in New York (UTC-5), subtract 5 hours: it's 10:00 AM there. If you're in Tokyo (UTC+9), add 9 hours: it's midnight (12:00 AM the next day).
Think About It
If you have a friend in Tokyo (UTC+9) and you live in Los Angeles (UTC-8), the time difference is 17 hours. When it's noon in LA, it's 5:00 AM the next day in Tokyo. Finding a good time to video chat requires creative scheduling!
Quick Check
1. How many primary time zones are there, based on 15-degree longitude intervals?
2. If it's 3:00 PM UTC on Monday, what time is it in Eastern Standard Time (UTC-5)?
3. What happens when you cross the International Date Line traveling westward?