Oscar Cullman:

Primitive Christianity knows nothing of a timeless God. The “eternal” God is he who was in the beginning, is now, and will be in all the future, “who is, who was, and who will be” (Rev. 1 :4) . Accordingly, his eternity can and must be expressed in this “naive” way, in terms of endless time.

https://www.scribd.com/doc/127918276/Cullmann-Christ-and-Time-the-Primitive-Christian-Conception-of-Time