w = 6(Y / 7)_r + 3((11 Y + 3) / 30)_r (rejecting sevens),
the values of which obviously circulate in a period of 7 times 30 or 210
years.
Let C denote the number of completed cycles, and y the year of the cycle;
then Y = 30 C + y, and
w = 5(C / 7)_r + 6(y / 7)_r + 3((11 y +3) / 30)_r (rejecting sevens).