Applications of world time zones
There are many possible applications, and one main area is communication. For example, when making phone calls (or video calls) with people in other countries, whether it be for business, or calling family and friends, we need to ensure we are calling at appropriate times.
We can use the GMT of the two people involved, or even just the time difference, for scheduling calls. Another way is to use a website, like www.timeanddate.com, which provides various tools for scheduling your time.
One way of doing this is by using the "Current Time" of cities around the world. The table below is an excerpt of the list they might provide:
| City | Current Time |
|---|---|
| Madrid | Fri $2:52$2:52 am |
| Managua | Thu $6:52$6:52 pm |
| Manila | Fri $8:52$8:52 am |
| Melbourne | Fri $10:52$10:52 am |
| Mexico City | Thu $7:52$7:52 pm |
| Miami | Thu $8:52$8:52 pm |
| Minneapolis | Thu $7:52$7:52 pm |
| Minsk | Fri $3:52$3:52 am |
| Montevideo | Thu $9:52$9:52 pm |
| Montreal | Thu $8:52$8:52 pm |
| Moscow | Fri $4:52$4:52 am |
| Mumbai | Fri $6:22$6:22 am |
From the table above we can see that the current time in Minsk is Fri $3:52$3:52 am, and the current time in Montevideo is Thu $9:52$9:52 pm. As it is currently Thursday in Montevideo, and it is currently Friday in Minsk, we can see that Minsk is ahead of Montevideo. More specifically, Minsk is $6$6 hours ahead of Montevideo.
Practice questions
Question 1
Valerie in Hobart has a phone conversation with Oprah in Manilla. Manilla is $2$2 hours behind Hobart time.
If Valerie calls at $10$10:$30$30am, what time is it for Oprah?
$\editable{}$:$\editable{}$am
If Oprah calls at $7$7:$30$30pm, what time is it for Valerie?
$\editable{}$:$\editable{}$pm
Question 2
The rugby World Cup final is broadcast live across the world. One particular year it was held in Wales and the game started at $4$4 pm local time. Where Beth lives, it is $17$17 hours behind Wales. At what time did the game start in her local time?
$\editable{}$pm
Calculating travel times between cities
When we're calculating how long a flight takes, we need to consider the local time in both cities. Similarly, if we want to know the local time in the departure/arrival city, we need to consider the time in one city and the flight time and then adjust the time based on time zones.
Practice questions
Question 3
A plane left airport A at $8$8:$30$30 pm on Tuesday and landed at airport B at $9$9:$00$00 pm (local time) on the same day.
If airport B is $19$19 hours behind airport A, how long did the trip take?
Question 4
When the time is $5$5:$23$23 pm in Honolulu, it is $10$10:$23$23 pm in Miami. You take 19 hours to travel from Honolulu to Miami.
If you leave at $4$4:$50$50 pm on Sunday:
At what time (local time) will you arrive in Miami?
$\editable{}$: $\editable{}$ pm
On what day will you arrive in Miami?
Sunday
ASaturday
BMonday
CTuesday
D
Question 5
The following table displays the departure and flight times for three Air China flights.
| Flight Number | Airport Code | Departure Time | Airport Code | Flight Time |
|---|---|---|---|---|
| CA994 |
San Francisco UTC -8 (SFO) |
$1$1:$13$13 pm |
Beijing UTC +8 (PEK) |
$12$12 hours and $31$31 mins. |
| CA927 |
Shanghai Pudong UTC +8 (PVG) |
$5$5:$56$56 pm |
Beijing UTC +8 (PEK) |
$8$8 hours and $31$31 mins. |
| CA950 |
Beijing UTC +8 (PEK) |
$7$7:$21$21 pm |
San Francisco UTC -8 (SFO) |
$14$14 hours and $37$37 mins. |
What time does CA994 arrive in Beijing local time?
$\editable{}$ : $\editable{}$ pm
What time does CA927 arrive in Beijing local time?
$\editable{}$ : $\editable{}$ am
What time does CA950 arrive in San Francisco local time?
$\editable{}$ : $\editable{}$ pm