/*
* Find an equivalent year for the one given, where equivalence is deterined by
* the two years having the same leapness and the first day of the year, falling
* on the same day of the week.
*
* This function returns a year between this current year and 2037, however this
* function will potentially return incorrect results if the current year is after
* 2010, (rdar://problem/5052975), if the year passed in is before 1900 or after
* 2100, (rdar://problem/5055038).
*/
int equivalentYearForDST(int year)
{
// It is ok if the cached year is not the current year as long as the rules
// for DST did not change between the two years; if they did the app would need
// to be restarted.
static int minYear = minimumYearForDST();
int maxYear = maximumYearForDST();
int difference;
if (year > maxYear)
difference = minYear - year;
else if (year < minYear)
difference = maxYear - year;
else
return year;
int quotient = difference / 28;
int product = (quotient) * 28;
year += product;
return year;
}
/*
* Find an equivalent year for the one given, where equivalence is deterined by
* the two years having the same leapness and the first day of the year, falling
* on the same day of the week.
*
* This function returns a year between this current year and 2037, however this
* function will potentially return incorrect results if the current year is after
* 2010, (rdar://problem/5052975), if the year passed in is before 1900 or after
* 2100, (rdar://problem/5055038).
*/
int equivalentYearForDST(int year)
{
// It is ok if the cached year is not the current year as long as the rules
// for DST did not change between the two years; if they did the app would need
// to be restarted.
static int minYear = minimumYearForDST();
int maxYear = maximumYearForDST();
int difference;
if (year > maxYear)
difference = minYear - year;
else if (year < minYear)
difference = maxYear - year;
else
return year;
int quotient = difference / 28;
int product = (quotient) * 28;
year += product;
ASSERT((year >= minYear && year <= maxYear) || (product - year == static_cast<int>(std::numeric_limits<double>::quiet_NaN())));
return year;
}
