final package com.thoughtworks.xstream.converters.extended;

import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;

import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;

/**
 * Converts a java.util.GregorianCalendar to XML. Note that although it currently only contains one field, it nests
 * it inside a child element, to allow for other fields to be stored in the future.
 *
 * @author Joe Walnes
 * @author J&ouml;rg Schaible
 */
public class GregorianCalendarConverter implements Converter {

    public boolean canConvert(Class type) {
        return type.equals(GregorianCalendar.class);
    }

    public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
        GregorianCalendar calendar = (GregorianCalendar) source;
        writer.startNode("time");
        long timeInMillis = calendar.getTime().getTime(); // calendar.getTimeInMillis() not available under JDK 1.3
        writer.setValue(String.valueOf(timeInMillis));
        writer.endNode();
        writer.startNode("timezone");
        writer.setValue(calendar.getTimeZone().getID());
        writer.endNode();
    }

    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
        reader.moveDown();
        long timeInMillis = Long.parseLong(reader.getValue());
        reader.moveUp();
        final String timeZone;
        if (reader.hasMoreChildren()) {
            reader.moveDown();
            timeZone = reader.getValue();
            reader.moveUp();
        } else { // backward compatibility to XStream 1.1.2 and below
            timeZone = TimeZone.getDefault().getID();
        }

        GregorianCalendar result = new GregorianCalendar();
        result.setTimeZone(TimeZone.getTimeZone(timeZone));
        result.setTime(new Date(timeInMillis)); // calendar.setTimeInMillis() not available under JDK 1.3

        return result;
    }

}

package com.thoughtworks.xstream.converters.extended;

import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;

import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;

/**
 * Converts a java.util.GregorianCalendar to XML. Note that although it currently only contains one field, it nests
 * it inside a child element, to allow for other fields to be stored in the future.
 *
 * @author Joe Walnes
 * @author J&ouml;rg Schaible
 */
public class GregorianCalendarConverter implements Converter {

    public boolean canConvert(Class type) {
        return type.equals(GregorianCalendar.class);
    }

    public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
        GregorianCalendar calendar = (GregorianCalendar) source;
        writer.startNode("time");
        long timeInMillis = calendar.getTime().getTime(); // calendar.getTimeInMillis() not available under JDK 1.3
        writer.setValue(String.valueOf(timeInMillis));
        writer.endNode();
        writer.startNode("timezone");
        writer.setValue(calendar.getTimeZone().getID());
        writer.endNode();
    }

    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
        reader.moveDown();
        long timeInMillis = Long.parseLong(reader.getValue());
        reader.moveUp();
        final String timeZone;
        if (reader.hasMoreChildren()) {
            reader.moveDown();
            timeZone = reader.getValue();
            reader.moveUp();
        } else { // backward compatibility to XStream 1.1.2 and below
            timeZone = TimeZone.getDefault().getID();
        }

        GregorianCalendar result = new GregorianCalendar();
        result.setTimeZone(TimeZone.getTimeZone(timeZone));
        result.setTime(new Date(timeInMillis)); // calendar.setTimeInMillis() not available under JDK 1.3

        return result;
    }

}

Fix weird "final" in package decl.