var day;
var month;
var year;

function openCalendar(form, field_Year, field_Month, field_Day, type) {
    window.open("calendar.php", "calendar", "width=300,height=140,status=no");
	YearField = eval("document." + form + "." + field_Year);
	MonthField = eval("document." + form + "." + field_Month);
	DayField = eval("document." + form + "." + field_Day);
    dateType = type;
}

/**

 * Formats number to two digits.
 *
 * @param   int number to format.
 */
function formatNum2(i, valtype) {
    f = (i < 10 ? '0' : '') + i;
    if (valtype && valtype != '') {
        switch(valtype) {
            case 'month':
                f = (f > 12 ? 12 : f);
                break;

            case 'day':
                f = (f > 31 ? 31 : f);
                break;

            case 'hour':
                f = (f > 24 ? 24 : f);
                break;
        }
    }

    return f;
}

/**
 * Formats number to four digits.
 *
 * @param   int number to format.
 */
function formatNum4(i) {
    return (i < 1000 ? i < 100 ? i < 10 ? '000' : '00' : '0' : '') + i;
}

/**
 * Initializes calendar window.
 */
function initCalendar() {
	dt = new Date();
	currentYear = dt.getFullYear();
	currentMonth = dt.getMonth();
	
    if (!year && !month && !day) {
        /* Called for first time */
        if (window.opener.YearField.value) {
			year = window.opener.YearField.value;
		} else {
			year = dt.getFullYear();
		}
		if (window.opener.MonthField.value) {
			month = window.opener.MonthField.value;
			month--; 
		} else {
			month = dt.getMonth();	
		}
		if (window.opener.DayField.value) {
			day = window.opener.DayField.value;
		} else {
			day = dt.getDate();
		}
    } else {
        /* Moving in calendar */
        if (month > 11) {
            month = 0;
            year++;
        }
        if (month < 0) {
            month = 11;
            year--;
        }
    }

	prevYear = 1;	
	prevMonth = 1;	
	if (currentYear == year) {
		prevYear = 0;	
		if (currentMonth == month) {
			prevMonth = 0;	
		}
	}
	
    if (document.getElementById) {
        cnt = document.getElementById("calendar_data");
    } else if (document.all) {
        cnt = document.all["calendar_data"];
    }

    cnt.innerHTML = "";

    str = ""

    //heading table
    str += '<table class="calendar"><tr><th width="50%" class="cMonthYear">';
    if (prevMonth == 1) {
		str += '<a href="javascript:month--; initCalendar();" class="cMonthYear">&laquo;</a> ';
	}
	str += month_names[month];
    str += ' <a href="javascript:month++; initCalendar();" class="cMonthYear">&raquo;</a>';
    str += '</th><th width="50%" class="cMonthYear">';
    if (prevYear == 1) {
		str += '<a href="javascript:year--; initCalendar();" class="cMonthYear">&laquo;</a> ';
	}
	str += year;
    str += ' <a href="javascript:year++; initCalendar();" class="cMonthYear">&raquo;</a>';
    str += '</th></tr></table>';

    str += '<table class="calendar"><tr>';
    for (i = 0; i < 7; i++) {
        str += '<th width="14%" class="cWeek">' + day_names[i] + "</th>";
    }
    str += "</tr>";

    var firstDay = new Date(year, month, 1).getDay();
    var lastDay = new Date(year, month + 1, 0).getDate();

    str += "<tr>";

    dayInWeek = 0;
    for (i = 0; i < firstDay; i++) {
        str += "<td>&nbsp;</td>";
        dayInWeek++;
    }
    for (i = 1; i <= lastDay; i++) {
        if (dayInWeek == 7) {
            str += "</tr><tr>";
            dayInWeek = 0;
        }

        dispmonth = 1 + month;

		selectYear = formatNum4(year);
		selectMonth = formatNum2(dispmonth, 'month');
		selectDay = formatNum2(i, 'day');
			
        if (i == day) {
            style = ' class="selected"';
        } else {
            style = '';
        }
		str += "<td" + style + "><a href=\"javascript:returnDate(" + selectYear + ", " + selectMonth + ", " + selectDay + ");\"" + style + ">" + i + "</a></td>"
        dayInWeek++;
    }
    for (i = dayInWeek; i < 7; i++) {
        str += "<td>&nbsp;</td>";
    }

    str += "</tr></table>";

    cnt.innerHTML = str;

}

/**
 * Returns date from calendar.
 */
function returnDate(Year, Month, Day) {
	window.opener.YearField.value = Year;
	window.opener.MonthField.value = Month;
	window.opener.DayField.value = Day;
    window.close();
}