Chapter 16-3

Which years became one day longer by the conference of the foolish Roman priests?
They were 38 B.C., 35 B.C., 32 B.C., 29 B.C., 26 B.C., 23 B.C., 20 B.C., 17 B.C., 14 B.C., and 11 B.C. The total was ten days.
On the other hand, which years became every one day shorter?
They were 5 B.C., 1 B.C., and A.D. 4 The total was three days.
10 - 3 = 7
In other words, as the seven days became longer than the usual winter solstice, on December 25 became the winter solstice. (The date shifted seven days on calendar).