// This code was developed by Keith Scott for Adge Cutler - www.lcars.org.uk
// Feel free to use this code, however no warranty is provided as to the accuracy
// of the coding.
// If you choose to use this, please include a link back to www.lcars.org.uk on your site.
// Thank you.   Keith Scott  07/09/2004

var DaysIntoYear = 0;
var DaysInYear = 0;
var Year = 0;
var Month = 0;
var Day = 0;
var Hour = 0;
var Minute = 0;
var StarDate = "";
var MonthDays = new Array();
var Data = "";

MonthDays[1] = 31;
MonthDays[2] = 28;
MonthDays[3] = 31;
MonthDays[4] = 30;
MonthDays[5] = 31;
MonthDays[6] = 30;
MonthDays[7] = 31;
MonthDays[8] = 31;
MonthDays[9] = 30;
MonthDays[10] = 31;
MonthDays[11] = 30;
MonthDays[12] = 31;

function Calculate() {
	if ( Data == "" ) Data = document.getElementById('Data');
	DaysIntoYear = 0;
	Year = 0;
	Month = 0;
	Day = 0;
	Hour = 0;
	Minute = 0;
	StarDate = "";
	var StarDatePattern = /^-?\d{4,7}\.\d{0,4}$/ 
	var DatePattern = /\d\d\/\d\d\/\d\d\d\d$/
	var DateTimePattern = /\d\d\/\d\d\/\d\d\d\d\s\d\d\S\d\d$/
	var DateValue = Data.value.substr(0,10);
	var TimeValue = Data.value.substr(11,5);
	if ( Data.value.match(DateTimePattern) ) {
		Check_Date(DateValue);
		Check_Time(TimeValue);
		if ( StarDate != "Invalid!" ) CalculateStarDate();
		return;
	}
	
	if ( Data.value.match(DatePattern) ) {
		Check_Date(DateValue);
		if ( StarDate != "Invalid!" ) CalculateStarDate();
		return;
	}

	if ( Data.value.match(StarDatePattern) ) {
		CalculateRealDate(Data.value);
		return;
	}

	alert("Invalid date format!");
}

function Check_Date(DateText){

	var err = 0;
	var leap = 0;
	Year = DateText.substr(6,4);
	Month = DateText.substr(3,2);
	Day = DateText.substr(0,2);
	if (Year == 0) {
		err = 20;
	}
	if ((Month < 1) || (Month > 12)) {
		err = 21;
	}
	if ((Day < 1) || (Day > 32)) {
		err = 22;
	}
	if ((Year % 4 == 0) || (Year % 100 == 0) || (Year % 400 == 0)) {
		leap = 1;
		MonthDays[2] = 29;
	}
	else {
		leap = 0;
		MonthDays[2] = 28;
	}
	if ((Month == 2) && (leap == 1) && (Day > 29)) {
		err = 23;
	}
	if ((Month == 2) && (leap != 1) && (Day > 28)) {
		err = 24;
	}
	if ((Day > 30) && ((Month == "04") || (Month == "06") || (Month == "09") || (Month == "11"))) {
		err = 26;
	}
	if (err == 0) {
		for ( i=1;i<Month;i++) {
			DaysIntoYear = DaysIntoYear + MonthDays[i];
		}
		DaysIntoYear = DaysIntoYear + (Day - 1);
		DateType = "Date"; 
		DaysInYear = 365;
		if ( leap == 1 ) DaysInYear = 366;
	}
	else {
		StarDate= "Invalid!"
	}
}

function Check_Time(TimeText) {

	Minute = TimeText.substr(3,2);
	Hour = TimeText.substr(0,2);
	if ( Hour > 23 || Minute > 59 ) DateType = "";
}

function CalculateStarDate() {

	var FirstPart = "";
	var MinutesPart = 0;
	var HoursPart = 0;
	var DaysPart = 0;
	var InterimDate = "";
	FirstPart = Year - 2323;
	MinutesPart = Minute / 60;
	HoursPart = ( ( Hour * 1 )+MinutesPart  ) / 24;
	DaysPart = ( parseInt(DaysIntoYear) + HoursPart ) / DaysInYear;
	DaysPart = DaysPart * 1000;
	InterimDate = FirstPart+""+DaysPart;
	StarDate = parseInt(InterimDate*10000)/10000;
	document.getElementById('Result').innerHTML = "Stardate: " + StarDate;
}

function CalculateRealDate(DateText) {

	var DatePart = "";
	var MinutesPart = 0;
	var HoursPart = 0;
	var DaysPart = 0;
	var MonthCount = 0;
	DatePart = DateText.substring(DateText.indexOf(".")-3,DateText.length+1);
	YearPart = DateText.substr(0,DateText.indexOf(".")-3);
	Year = 2323 + parseInt(YearPart);
	if ((Year % 4 == 0) || (Year % 100 == 0) || (Year % 400 == 0)) {
		MonthDays[2] = 29;
		DaysInYear = 366;
	}
	else {
		MonthDays[2] = 28;
		DaysInYear = 365;
	}
	DatePart = DatePart/1000;
	DaysIntoYear = parseInt(DatePart*DaysInYear);
	Hours = parseInt(((DatePart*DaysInYear)-DaysIntoYear)*24);
	Minutes = parseInt(((((DatePart*DaysInYear)-DaysIntoYear)*24)-Hours)*60);
	for (i=1;i<13;i++) {
		if ( DaysIntoYear < MonthDays[i] ) {
			i = 13;
		}
		else {
			DaysIntoYear = ( DaysIntoYear - MonthDays[i]);
			MonthCount++;
		}
	}
	DaysIntoYear++;
	MonthCount++;
	Day = "0"+DaysIntoYear;
	Day = Day.substr(Day.length-2,2);
	Month = "0"+MonthCount;
	Month = Month.substr(Month.length-2,2);
	Hour = "0"+Hours;
	Hour = Hour.substr(Hour.length-2,2);
	Minute = "0"+Minutes;
	Minute = Minute.substr(Minute.length-2,2);
	DateText = Day+"/"+Month+"/"+Year+" "+Hour+":"+Minute;
	document.getElementById('Result').innerHTML = "Calendar date: " + DateText;
}

function TodayAsStarDate() {

	var weekDayName = new Array ("Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday")
	var curDate = new Date();
	Day = "0"+curDate.getDate();
	Day = Day.substr(Day.length-2,2);
	Month = "0"+(curDate.getMonth()+1);
	Month = Month.substr(Month.length-2,2);
	Year = curDate.getYear();
	if (Year < 2000) Year += 1900; //for Netscape
	Hour = "0"+curDate.getHours();
	Hour = Hour.substr(Hour.length-2,2);
	Minute = "0"+curDate.getMinutes();
	Minute = Minute.substr(Minute.length-2,2);
	var Weekday = weekDayName[curDate.getDay()];
	Today = Day+"/"+Month+"/"+Year+" "+Hour+":"+Minute;
	Check_Date(Today);
	var FirstPart = "";
	var MinutesPart = 0;
	var HoursPart = 0;
	var DaysPart = 0;
	var InterimDate = "";
	FirstPart = Year - 2323;
	MinutesPart = Minute / 60;
	HoursPart = ( parseInt(Hour)+MinutesPart  ) / 24;
	DaysPart = ( parseInt(DaysIntoYear) + HoursPart ) / DaysInYear;
	DaysPart = DaysPart * 1000;
	InterimDate = FirstPart+""+DaysPart;
	StarDate = parseInt(InterimDate*10000)/10000;
	document.write("<font Class=StarDate>Today is <I>" + Weekday + " " + Day+"/"+Month+"/"+Year+"</I> Time <I>"+Hour+":"+Minute + "</I><BR>Stardate: <I>" + StarDate + "</I></FONT>");
}