ObserverTimezone is necessary?

[stenza]

Hi,

I don't have any experience in solar calculations.

I got confused a bit:
Based on the example, we need to set the following arguments:

• setObserverPosition
• setObserverDate
• setObserverTime

As their name implies, these are local dates and local times of the observer.

Then why do I need to give the ObserverTimezone?

Furthermore, how can I calculate the timezone from a LatLong coordinate for those exotic places close to the date line, where some island belongs to different timezone as they have these zigzag timezone border?

Even further, I believe the observer's local time with the lat/long coordinates is the most accurate, because with those it is easier and more precise to calculate the Earth's UTC time, and then we can have the Observer sunset, rather than the timezone sunset.

The point is, how can I calculate the Sun position without Timezone information?
(I don't need to know the local sunset, or anything else, I need only the Sun azimuth and alt)

Can anyone shed some light on that?