Relative Timezones: Questions and Answers

1. Other timezone lists say that New South Wales is 10 hours ahead of Britain. Why does your list say that New South Wales is 11 hours ahead of Britain in January, but 9 hours ahead in July?
   During Northern Hemisphere Summer, Britain's clocks are advanced by one hour.
   During Southern Hemisphere Summer, New South Wales' clocks are advanced by one hour.
   So the time difference is never 10 hours, except for on the days when the clocks change (New South Wales changes its clocks about 11 hours before Britain does).
   
   
2. During the second half of the year, California is 8 hours behind Britain, and Irkutsk (Russia) is 8 hours ahead of Britain. So Irkutsk should be 16 hours ahead of California. Why is Irkutsk listed as being only 15 hours ahead of California during a single day in October?
   California and Irkutsk both put their clocks back on the last Sunday morning in October.
   But Sunday comes 16 hours earlier in Irkutsk, so for 16 hours Irkutsk has put its clocks back and California hasn't.
   This 16 hour period is Sunday in Irkutsk, but Saturday in California.
   So relative to Irkutsk, California is only 15 hours behind for a single Sunday in October.
   Relative to California, Irkutsk is only 15 hours ahead for a single Saturday in October.

   In compiling this list, I have made the arbitrary decision that

   • places whose winter times are less than 13 hours apart are on the same day (e.g. UK and Irkutsk, or UK and California)
   • places whose winter times are 13 hours apart or more are on different days (e.g. California and Irkutsk).

   This causes many odd effects, for instance when comparing the time in various Russian places with respect to Greenland, but it is the best way of meeting the needs of people who phone companies around the world in business hours. Another solution would be to state the exact time when the clocks change in the other country, but that would vastly increase the amount and complexity of data, because it would then become necessary to clutter the list with unimportant details such as the fact that Moscow is three hours ahead of London all year around except for two hours in the middle of the night on two days of the year.

3. Lord Howe Island is listed as putting its clocks forward by 30 minutes in summer. Is that a mistake?
   No.
   
   
4. This is boring. Why did you do it?
   I was hoping you weren't going to ask that. Well, I was a professional C++ programmer, and I wrote the program which produces the HTML files for fun. If I'd known in advance how hard it is to gather accurate timezone data, I probably wouldn't have bothered starting. It was going to be a Java applet, but I don't think an applet can print on paper. So I settled for a full Java application which outputs about 170 HTML files.
   
   
5. Why Finnish?
   I wanted to write a multilingual program. My first choice was Dutch, but this would be pointless because most Dutch people speak English, and country names in Dutch and English are nearly always mutually intelligible anyway (Switzerland = Zwitserland, Sweden = Zweden etc). Finnish is the only major European language which uses the Latin alphabet but is different enough from English to make a timezone list worth producing. However, I can't help thinking that the page which lists the timezones of the world in Finnish relative to Pitcairn Island may be the least useful and least interesting page on the whole web. After completing the Finnish version, I nearly finished a Russian version, and it was fun to see my program outputting HTML files in Cyrillic (KOI8). This would be a useful resource because a lot of Russian speakers can't even read the Latin alphabet, but I don't have the time to finish it at the moment.