// Code from the Zune music player.
// On Dec 31, 2008, all Zunes stopped working!
// Explanation: http://www.zuneboards.com/forums/showthread.php?t=38143

// Some dates to test with:
// today: System.currentTimeMillis()
// Dec 30, 2008: 1230624000000l
// Dec 31, 2008: 1230710400000l
// Jan 1, 2009: 1230850800000l
// Jan 1, 2011: 1293922800000l
// Dec 31, 2011: 1325372400000l

// Many computer systems keep track of time as number of seconds since Jan 1, 1970.
// This program takes a time in this form and determines the corresponding
// year and day of the year. For a non-leap year, the day-of-year will be between 1 and 365.
// For a leap year, it will be between 1 and 366.

public class DaysBad {
	public static final int ORIGIN_YEAR = 1970;
	
	public static void main(String[] args) {
		long millis = 1230710400000l;  // Dec 31, 2008
		
		// we subtract 1/3 to account for Pacific Time being 8 hours
		// behind Greenwich Mean Time
		double days = millisToDays(millis) - 1.0 / 3.0;
		
		// we add 1 because 1/1/70 is day 1 of 1970, not day 0
		int day = (int) days + 1;
		int year = ORIGIN_YEAR;
		
		while (day > 365) {		// on the 366th day of a leap year, we get stuck!
			if (isLeap(year)) {
				if (day > 366) {	// 366 is NOT bigger than 366, fail the test
					day = day - 366;
					year++;
				} 
			} else {
				day = day - 365;
				year++;
			}
		}
		
		System.out.println("millis = " + millis);
		System.out.println("days   = " + days);
		System.out.println("year   = " + year);
		System.out.println("day    = " + day);
	}
	
	// returns whether or not a year is a leap year
	public static boolean isLeap(int year) {
		return year % 4 == 0;
	}
	
	// converts milliseconds to days
	public static double millisToDays(double millis) {
		return millis / 1000.0 / 60.0 / 60.0 / 24.0;
	}
}