The church fathers also unanimously teach it:
Six thousand years of our world are not yet completed.
St. Jerome, Doctor of the Church, Commentariorum in Epistulam Pauli Apostoli ad Titum Liber Unus, I,Ib-4.
> Six thousand years of our world are not yet completed.
Council of Trullo, canon 3,
>Especially as the fault of ignorance has reached no small number of men, we decree, that those who are involved in a second marriage, and have been slaves to sin up to the fifteenth of the past month of January, in the past fourth Indiction, the 6109th year, and have not resolved to repent of it, be subjected to canonical deposition…
The Acts of the Second Council of Nicaea (AD 787), Sess. 6:
>“In the year 5501 Christ our God came to mankind and lived with us for thirty-three years and a little less than five months.”
St. Basil the Great (c. 330–379):
>"And if anyone were to say that the days mentioned in the account are not to be understood as days, he would be admitting that the sacred Scriptures are not true. For they would be saying that there were no six days, but only a confused time… the evening and the morning were the first day."
Source: Hexaemeron, Homily 1, trans. Blomfield Jackson (The Macmillan Company, 1895), p. 23.
St. John Chrysostom (c. 349–407):
>"In the first place, He [God] created light, and then darkness; He divided the light from the darkness, calling the light 'day,' and the darkness He called 'night.' And the evening and the morning were the first day… This, then, is the meaning of the expression, ‘and the evening and the morning were the first day.’ He made a day as we understand it today, with an evening and a morning."
Source: Homily on Genesis, Homily 1, trans. Roy J. Deferrari (Catholic University of America Press, 1951), p. 21.*
St. Ephraim the Syrian (c. 306–373):Post too long. Click here to view the full text.