Treebeard's Homepage : Stumpers

Treebeard's Stumper Answer
16 February 2001

Julie Time

My wife Julie is trekking in Thailand with her friend Debora. We communicate with frequent email, but the time difference is still a challenge after two weeks. Julie's flight schedule is even more confusing! Offhand, it takes them a day and a half to fly there and only two hours to get back! Of course time zones and the International Date Line are involved. According to my atlas, we are at GMT -8 hours, Taiwan is +8 and Thailand is +7 hours. How long will the flight take in Julie time? Will she feel like driving home after landing in LA?

Julie is sharing her adventures by email on the DMS Julie in Thailand page.

Here's Julie and Debora's flight plan to and from Bangkok in Thailand, with a stop in Taiwan. How long are they in the air, both there and back again? These days and times look like a misprint!

 
  From: To: Depart: Arrive:
 
There: Los Angeles, California Taipei, Taiwan Thursday
2:10 PM
Friday
8:40 PM
 
  Taipei, Taiwan Bangkok, Thailand Friday
9:55 PM
Saturday
12.45 AM

Back again: Bangkok, Thailand Taipei, Taiwan Thursday
4:25 PM
Thursday
8:55 PM
 
  Taipei, Taiwan Los Angeles, California Thursday
11:10 PM
Thursday
6:30 PM


Julie and Debora flew between LA (GMT -8) and Taiwan (+8) and Bangkok (+7). Thailand is 15 hours ahead of California (PST) time, the difference between +7 and -8. We're also 4 hours behind the International Date Line, and Thailand is 5 hours past it, a difference of 9 hours. But 15 + 9 = 24, so it comes to the same thing. I can subtract 9 hours or add 15 hours to get Thailand time. Julie and I both had to think about when today becomes tomorrow or yesterday. Minds and bodies get confused. World travel would be a lot easier if we all stayed at home!

I converted all of Julie's There times to California time by adding 8 or 9 hours. I converted her Back times to Bangkok time by subtracting 1 or 9 hours. This has been Julie time. I've had lots of practice in the last few weeks trying to synchronize our phone calls and email, and it never got easy!

  From: To: Depart: Arrive: Flight Time: Total Air
Time:
 
 
There: Los Angeles,
California
Taipei,
Taiwan
Thursday
2:10 PM
Friday
8:40 PM
   
      +0 hours
-------------
2:10
+8 hours
-------------
16:40
  16:40
-   2:10
---------
 
    Julie Time:
(California)
Thursday
2:10 PM
Friday
4:40 AM
14:30 hours  
 
  Taipei,
Taiwan
Bangkok,
Thailand
Friday
9:55 PM
Saturday
12.45 AM
   
      +8 hours
-------------
17:55
+9 hours
-------------
21:45
  21:45
- 17:55
----------
  14:30
+  3:50
----------
    Julie Time:
(California)
Thursday
5:55 AM
Friday
9:45 AM
3:50 hours 18:20 hours

Back: Bangkok,
Thailand
Taipei,
Taiwan
Thursday
4:25 PM
Thursday
8:55 PM
   
      - 0 hour
-------------
4:25
- 1 hour
-------------
7:55
  7:55
- 4:25
---------
 
    Julie Time:
(Thailand)
Thursday
4:25 PM
Thursday
7:55 PM
3:30 hours  
 
  Taipei,
Taiwan
Los Angeles,
California
Thursday
11:10 PM
Thursday
6:30 PM
   
      - 1 hour
-------------
10:10
- 9 hours
-------------
9:30
    9:30 + 12
- 10:10
---------
  11:20
+  3:30
----------
    Julie Time:
(Thailand)
Thursday
10:10 PM
Friday
9:30 AM
11:20 hours 14:50 hours

Notes:

I expected Julie to arrive at LAX at 6:30 PM (PST), which would feel like 9:30 AM in Julie time, so I hoped she would feel like driving home. In fact, their flight from Taiwan was delayed 8 hours because of fog. Julie and Debora finally got off the ground at 7:30 AM (Julie time in Taiwan) and they arrived in LA at 2:15 AM local time after 11 hours in the air. They waited until (LA) morning to drive to my parents' house where Julie's car was parked. But 7:00 AM in California was 10:00 PM Julie/Thailand time, time to crash. So much for my romantic plans! Julie did make it home that evening, and it took several days to adjust to home time. Coming home (west-to-east) was quicker, but it was definately harder for Julie and Debora than going there (east-to-west). I'm sure that flight delay had a lot to do with it. I guess I'm glad the Taipei airport is more concerned with safety than schedules.

Coordinating times across the International Date Line does not always mean changing the day. I made this little chart to help understand Julie's email times:

Santa Barbara 12 AM 3 AM 6 AM 9 AM 12 PM 3 PM 6 PM 9 PM
Thailand 3 PM 6 PM 9 PM 12 AM 3 AM 6 AM 9 AM 12 PM
  same day different day

World time zones weren't needed until the 1880s when fast railroad travel across the country finally required a better way of keeping track of schedules. The legacy is that all flight times are local to the airport. Graybear forwarded this account from the Smithsonian National Museum of American History:

In 1881, railroad managers commissioned William Frederick Allen to devise a plan that coordinated the train connections between fifty different regional times. Allen proposed to cut down the time zones to five. Each zone was determined by the time at the central meridian within each zone. Each central meridian was fifteen degrees of longitude or one hour apart. Prior to 1883, there were no time zones as we know them now. Each town and city had independent set times depending on their observation of the sun.

On November 18, 1883, Standard Railway Time went into effect. Most railroads and communities switched to standard time therefore having two noons byy local time and by standard time. Some people objected to the change in time because it represented a loss of local autonomy or a disregard for the authority of nature. Some communities initially refused to switch.

By 1884, delegates to the International Meridian Conference recommended that the globe be divided into twenty-four time zones, each one hour apart. This coordinated time system was slowly adopted over the world.

360 degrees (around the earth) divided by 24 hours (per day) = 15 degrees per hour. But it's not that simple! No one wants their city and country divided unnecessarily, so there are actually more than 24 time zones! (Click on the map for a more readable version from the U.S. Naval Observatory.)

Stumpers remain. Why Greenwich, England? Why are India and a few other countries 30 minutes offset from the rest of the world? Why is China one time zone instead of five? Why is GMT time also called "Zulu time"? What time is it at Anarctica and the North Pole and the International Space Station that are all off the map?

Here's another tricky time zone stumper from Graybear:

Recently this telephone conversation took place in the continental U.S.:
      A: "What time is it where you live?"
      B: "1:30"
      A: "That's what time it is here, also, but I'm in a west coast state and you are in an east coast state!"
      B: "How can that be?????"
(Answer)

Here are some links for your own research about international travel:

Back to Stumper


Last modified .

Copyright © 2001 by Marc Kummel / mkummel@rain.org