location specifier for hebrew date js

Hi

I love your API's, and am using them for electronic display boards and soon the website for our shul.

For the scripts hdate-he.js and hdate-en.js, there is no location specifier. I have noticed as I use these, that the hebrew date does not turn over at Shkia or Tzeit HaKochavim, or even later into the evening. I am at GMT+02:00

On what location is the date calculation based?

Is there a way to specify a location to use?

Can the date turn over at Night-fall?

Regards

Aryeh Leib