function calendar(date){
    //If no parameter is passed use the current date.
    if(date == null)
        date = new Date();

    day = date.getDate();
    month = date.getMonth();
    year = date.getFullYear();

    months = new Array('Janeiro',
                        'Fevereiro',
                        'Março',
                        'Abril',
                        'Maio',
                        'Junho',
                        'Julho',
                        'Agosto',
                        'Setembro',
                        'Outubro',
                        'Novembro',
                        'Dezembro');

    this_month = new Date(year, month, 1);
    next_month = new Date(year, month + 1, 1);

    //Find out when this month starts and ends.         
    first_week_day = this_month.getDay();
    days_in_this_month = Math.floor((next_month.getTime() - this_month.getTime()) / (1000 * 60 * 60 * 24));

    calendar_html = '<table style="background-color:666699; color:ffffff;" border="1">';

    calendar_html += '<tr><td colspan="7" align="center" style="background-color:9999cc; color:000000;">' + 
    months[month] + ' ' + year + '</td></tr>'

    calendar_html += '<tr>';

    //Fill the first week of the month with the appropriate number of blanks.       
    for(week_day = 0; week_day < first_week_day; week_day++){
        calendar_html += '<td style="background-color:9999cc; color:000000;">&nbsp;</td>';   
    }

    week_day = first_week_day;
    for(day_counter = 1; day_counter <= days_in_this_month; day_counter++){
        week_day %= 7;

        if(week_day == 0)
            calendar_html += '</tr><tr>';

        //Do something different for the current day.
        if(day == day_counter)   
            calendar_html += '<td align="center"><b>' + day_counter + '</b></td>';
        else
            calendar_html += '<td align="center" style="background-color:9999cc; color:000000;">&nbsp;' + 
        day_counter + '&nbsp;</td>';

        week_day++;
    }

    calendar_html += '</tr>';
    calendar_html += '</table>';

    //Display the calendar.     
    document.write(calendar_html);                  
}