The Zune's real-time clock stores the time in terms of days and seconds since January 1st, 1980. When the Zune's clock is accessed, the driver turns the number of days into years/months/days and the number of seconds into hours/minutes/seconds. Likewise, when the clock is set, the driver does the opposite.
The Zune frontend first accesses the clock toward the end of the boot sequence. Doing this triggers the code that reads the clock and converts it to a date and time. Below is the part of this code that determines the year component of the date:
Code:
year = ORIGINYEAR; /* = 1980 */
while (days > 365)
{
if (IsLeapYear(year))
{
if (days > 366)
{
days -= 366;
year += 1;
}
}
else
{
days -= 365;
year += 1;
}
}
Under normal circumstances, this works just fine. The function keeps subtracting either 365 or 366 until it gets down to less than a year's worth of days, which it then turns into the month and day of month. Thing is, in the case of the last day of a leap year, it keeps going until it hits 366. Thanks to the if (days > 366), it stops subtracting anything if the loop happens to be on a leap year. But 366 is too large to break out of the main loop, meaning that the Zune keeps looping forever and doesn't do anything else.
The unfortunate part is that there isn't anything that can be done to fix this besides somehow changing what the clock is set to (which is exactly what the battery disconnection trick ends up doing). On the other hand, it shows that Microsoft is correct: tomorrow, everyone's Zunes will operate normally again. However, if Microsoft doesn't fix this part of the firmware, the whole thing will happen all over again in 4 more years.. Hopefully by then a fix will be in place.
Z2K9 - Zune 30GB massive failing at stroke of midnight 31.12.
Re: Z2K9 - Zune 30GB massive failing at stroke of midnight 31.12.