Hi,
Thank you for your answers David G. Johnston and Tom Land. That is much more clear now.
Yet, there is one tiny thing left:
1. select TIMESTAMP WITH TIME ZONE '2004-10-19 10:23:54+03' at time zone 'America/Denver';
2004-10-19 01:23:54
2. select TIMESTAMP WITH TIME ZONE '2004-10-19 10:23:54+03' at time zone 'UTC+7';
2004-10-19 00:23:54
3. select TIMESTAMP WITH TIME ZONE '2004-10-19 10:23:54+03' at time zone 'Europe/Moscow';
2004-10-19 11:23:54
4. select TIMESTAMP WITH TIME ZONE '2004-10-19 10:23:54+03' at time zone 'UTC-3';
2004-10-19 10:23:54
The outputs of the 1st and the 2nd queries should be the same because "+/-" works opposite of ISO - 8601. Same thing should apply to query 3rd and 4th.
When I try following queries they give exactly the same output.
select now()::timestamp with time zone at time zone 'America/Denver';
select now()::timestamp with time zone at time zone 'UTC+7';
So, it should be related to the date. Yet, as you can see '2004-10-19 10:23:54+03' is nearly the same time of the year 18 years and 4 months ago. So, the same DST rules should apply, but it does not. There is 1 hour difference between query 1st and 2nd, also query 3rd and 4th.
What could be the reason for this?
Thanks!
Umut Tekin
