Microsoft has just shown the world what the consequences of a relatively small programming mistake can be. In this case, it’s a classic “off-by-one” error in the clock driver of the Zune mediaplayer:

year = ORIGINYEAR; /* = 1980 */

while (days > 365)
{
    if (IsLeapYear(year))
    {
        if (days > 366)
        {
            days -= 366;
            year += 1;
        }
    }
    else
    {
        days -= 365;
        year += 1;
    }
}

The code above converts the internal “seconds since 1980” time to something more readable, but on the last day of a leap year the number of days will be exactly 366, and thus it will stay in the loop until 24 hours later. While this is not a security risk, it does show how easy it is to make these kinds of mistakes. This is a simple piece of code, and even then it took me a while to figure out what the problem was.

YARPP