LYC
if (t2 >= ((2100 - 1980) / 4 * LYC + FEB))
l = t2 / LYC;
t2 -= l * LYC;
day += LYC * ((dd >> 11) & 0x1f);
if (day >= ((2100 - 1980) / 4 * LYC + FEB))