var tzwhere = require('tzwhere')
tzwhere.init();

var whiteHouse = {'lat': 38.897663, 'lng': -77.036562};

// Determine the timezone of the White House
console.log(tzwhere.tzNameAt(whiteHouse['lat'], whiteHouse['lng']));

// Determine the current offset from UTC, in milliseconds, of the White House's timezone
console.log(tzwhere.tzOffsetAt(whiteHouse['lat'], whiteHouse['lng']));

...
tzwhere.tzNameAt(whiteHouse['lat'], whiteHouse['lng'], function (error, result) {
	if (error) {
		console.log(error);
	} else {
		console.log(result);
	}
}
...

var tzwhere = require('tzwhere')
tzwhere.init('path/to/alternative/tz/file');

...