Using the Epoch, TimeZones and Calendars

Question

I hope someone can help, I've lost the afternoon trying to explain this so I can rely on the java date behaviour
the following code
         Calendar calendarGB_Eire = Calendar.getInstance(TimeZone.getTimeZone("GB-Eire"));
         Calendar calendarGMT = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
         Date date = new Date(0);
         calendarGMT.setTime(date);
         System.out.println(calendarGMT.get(Calendar.HOUR) + ":" + calendarGMT.get(Calendar.MINUTE));
         calendarGB_Eire.setTime(date);
         System.out.println(calendarGB_Eire.get(Calendar.HOUR) + ":" + calendarGB_Eire.get(Calendar.MINUTE));
         SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
         sdf.setCalendar(calendarGMT);
         System.out.println("GMT=" + sdf.format(date));
         sdf.setCalendar(calendarGB_Eire);
         System.out.println("GB=" + sdf.format(date));outputs
0:0
1:0
GMT=01/01/1970 00:00:00
GB=01/01/1970 01:00:00
See the 1 hour discrepancy?
On the 1st January the GB timezone is not in DST so should be using GMT hence the Epoch 00:00:00 1/1/1970 should display the same in both calendars. Not so? even if I have misunderstood and it is using the DST setting at the current time it is still wrong as at the time of writing the GB timezone is not in DST.

Answer 1

KPSeal, outstanding!
Sorry to say I didn't find that, it would have saved me an afternoon, in case anyone else wanders past with the same issue, here is the explanation of the Java behaviour.
"During the Second World War, double summer time (2 hours in advance of GMT) was introduced and was used for the period when, normally ordinary summer time would have been in force. During the winter clocks were kept one hour in advance of GMT. After the war, summer time was invoked each year from 1948 to 1967. In 1968 clocks were advanced one hour ahead of GMT on 18 February and remained so until British Standard Time, during which clocks were kept in advance of GMT all year, came into force between 27 October 1968 and 31 October 1971."
Message was edited by:
rsommerville