Of course it is possible, I never said it wasn't.
But I do pointed out that such a feature isn't that trivial and easy to implement just like that as how it first was portrayed, hence why I posted my previous reply.
As you pointed out, there are also other things to consider when creating such a plugin other than simply adding a field where you put the GMT offset in. And because of the nature of time offsets, it is as good as impossible to do everything automatically without much user input as it first was requested.
It indeed requires a lot of user input (filling in all the variables) and this input needs to be redone each year from scratch btw. But once this is done, it could run nicely.
But because of this, the question rises weither this is a good thing to do; the right way to follow... Isn't there a better method for all this? eg: instead of putting all those variables in, put 1 variable in connected to a website which does have all this info updated (DSTs) and check from there. One sush website is
http://www.timeanddate.com/worldclock/
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