Short sample using geotools for Java to determine timezone of Busingen (using http://efele.net/maps/tz/world/)

Main.java

package tzshapeparser;

import java.io.*;
import java.util.*;

import org.geotools.data.*;
import org.geotools.data.simple.SimpleFeatureSource;
import org.geotools.feature.*;
import org.geotools.geometry.jts.*;
import org.opengis.feature.simple.*;

import com.vividsolutions.jts.geom.*;

public class Main {
	// http://efele.net/maps/tz/world/
	public static void main(String[] args) throws Exception {
		File file = new File("world/tz_world.shp");
		com.vividsolutions.jts.geom.GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory(null);
		Coordinate coord = new Coordinate(8.689098, 47.703077); // longitude, latitude
		Point busingen = geometryFactory.createPoint(coord);
		Map<String, Object> params = new HashMap<>();
		params.put("url", file.toURI().toURL());
		DataStore dataStore = DataStoreFinder.getDataStore(params);
		SimpleFeatureSource featureSource = dataStore.getFeatureSource(dataStore.getTypeNames()[0]);
		FeatureIterator<SimpleFeature> iterator = featureSource.getFeatures().features();
		try {
			while (iterator.hasNext()) {
				SimpleFeature feature = iterator.next();
				Geometry sourceGeometry = (Geometry) feature.getDefaultGeometryProperty().getValue();
				if (sourceGeometry.contains(busingen)) {
					System.out.println(feature.getProperty("TZID").getValue().toString());
				}
			}
		} finally {
			iterator.close();
		}
	}
}

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>tzshapeparser</groupId>
	<artifactId>TZShapeParser</artifactId>
	<version>1.0-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>TZShapeParser</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<geotools.version>14.3</geotools.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.11</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.geotools</groupId>
			<artifactId>gt-shapefile</artifactId>
			<version>${geotools.version}</version>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>2.3.2</version>
				<configuration>
					<source>1.7</source>
					<target>1.7</target>
				</configuration>
			</plugin>
			<plugin>
				<artifactId>maven-eclipse-plugin</artifactId>
				<version>2.9</version>
				<configuration>
					<buildOutputDirectory>bin</buildOutputDirectory>
					<downloadSources>true</downloadSources>
					<testSourcesLast>true</testSourcesLast>
				</configuration>
			</plugin>
		</plugins>
	</build>

	<repositories>
		<repository>
			<id>maven2-repository.dev.java.net</id>
			<name>Java.net repository</name>
			<url>http://download.java.net/maven/2</url>
		</repository>
		<repository>
			<id>osgeo</id>
			<name>Open Source Geospatial Foundation Repository</name>
			<url>http://download.osgeo.org/webdav/geotools/</url>
		</repository>
	</repositories>
</project>