Changing Time Zones

Date: 11/17/1999 at 11:41:06
From: Caroline Reynolds
Subject: Time zones

1) An airplane left New York at 09:15 to travel to London. If the 
   flight took 5 hrs. 45 min., what was the local time when the plane 
   landed in London?

2) When it is midnight on Sunday in London, what time is it at 165 
   degrees west longitude?

Date: 11/17/1999 at 12:58:22
From: Doctor Rick
Subject: Re: Time zones

Hi, Caroline.

1) Here you have 2 steps: (a) add 5 hr. 45 min. to 09:15. (b) You're 
still on New York time, so convert to London time by adding or 
subtracting the correct number of hours.

2) If you pretend that each time zone is just a band of longitudes, 
then you can figure it out by math. To be sure you're right, you'd 
have to look on a map; and then you might find that which time zone 
you're in depends on your latitude.

Each time zone (a difference of 1 hour in local time) is 15 degrees 
wide. How many time zones are there between 0 degrees and 165 degrees 
longitude? 

Then you need to decide whether you add or subtract hours. Remember 
that the sun "moves" from east to west, so as you go west, noon (or 
any other time) comes later. At any one moment, the time is earlier to 
the west. I live near New York, for instance, and I know that when 
it's midnight in London, it's 7 PM here.

- Doctor Rick, The Math Forum
  http://mathforum.org/dr.math/