Goldstein goes on to speculate that the Maccabees decided to wait beyond Tishri, (The month of the autumn festivals), until Kislev since, because of the missed calendar intercalations, Kislev now fell when the autumn festivals should have been.

Assuming that God would perform His miracles at the right time and not be bound by an imperfect calendar, Judas and his men had to wait through two more months.

But the miracles still hadn't happened, even by the 23rd of Kislev, which would have been the last festive date if the intercalations had been done.

They needed 2 days to prepare for the ceremony, and this explains why it took place on 25th Kislev.

There was a precedent of sorts: I Kings 8:2 and 8:65, taken together, would have suggested that King Solomon doubled the length of the festival of Tabernacles for the dedication of the first Temple.