🔍 Key Concepts

• Zone description (ZD) and how its sign (+/-) relates to Greenwich Mean Time (GMT) or Universal Time (UT/GMT) • How to convert from GMT to zone time when given a negative ZD (e.g., -13) • How crossing the International Date Line or moving past 24 hours affects the calendar date

💭 Think About

• Are you moving east or west in time when the zone description is negative, and does that make local time earlier or later than GMT? • When you apply a -13 hour correction to 0152 GMT, do you pass midnight, and in which direction does the date change? • After adjusting the time by 13 hours, does the resulting local time still fall on 10 January, or does it become 9 January or 11 January?

✅ Before You Answer

• Make sure you apply the correct sign of the ZD: decide if you should add or subtract 13 from GMT to get local zone time. • After changing the time, check carefully whether you crossed 0000 (midnight) and in which direction, to determine the correct date change. • Confirm that your final answer’s time and date combination matches your computed local time and the proper day (before or after 10 January).