In the local time of each, during what times of the 24-hour day in January, and in July, is it the same day of the week in Canberra and in Honolulu? Canberra goes on daylight savings time in summer but Honolulu does not. Standard time in Canberra is GMT plus 10 hours, whereas Honolulu time is GMT minus 10 hours.

What would the answer be if somehow (by magic, perhaps) Australia and Hawaii were to be moved so that standard time in Canberra was GMT plus 12 hours and time in Honolulu was GMT minus 12 hours?

How would the answers to the questions above be affected if the International Date Line were moved to the prime meridian instead of being (roughly) directly opposite as it now is?

How GMT and DST govern the respective locations, Honolulu and Canberra, can change over time, the answers given pertain to the year of this posting. 

Answer to the first question:
In January, Canberra observes DST, and thus is at GMT+11 while Honolulu is at GMT-10. The two locations observe the same day during the following times.
Honolulu -- 00:00:00 (Midnight) to 03:00:00
Canberra -- 21:00:00 to 24:00:00 (Midnight)     

In July, Canberra is at standard GMT+10 while Honolulu remains at GMT-10, thus they observe the same day during the following times:
Honolulu -- 00:00:00 (Midnight) to 04:00:00
Canberra -- 20:00:00 to 24:00:00 (Midnight)

Answer to the second question:
Moving Canberra, Austrailia into time zone GMT+12 (IDLE: International Date Line East) and Honolulu, Hawaii into time zone GMT-12 (IDLW: International Date Line West) would effectively permit the two areas to only share the time called Midnight.  In January, where Canberra observes a GMT+13 due to a recognition of Daylight Saving Time, even this cusp would not observed.

Answer to third question: 
As the prime meridian passes largely through the middle of the time zone identified as GMT+0 and the International Date Line seperates two time zones IDLE (GMT+12) and IDLW (GMT-12), it would be necessary to know whether this IDL divides the current GMT+0 time zone into an E and W time zone and combines the current IDLE and IDLW into a new GMT+0 time zone or otherwise.  In any case, the third question does not provide enough information to give a definitive answer. 

Richard can you give more definitive information for the third part? 

Posted by Dej Mar on 2006-07-11 23:59:46