'Fifteenth' in the Bible

It came to pass also in the twelfth year, in the fifteenth day of the month, that the word of Jehovah came unto me, saying,

In the seventh month , in the fifteenth day of the month, in the feast, shall he do the like the seven days; according to the sin-offering, according to the burnt-offering, and according to the meal-offering, and according to the oil.