Full Idea
Saying 'God is eternal' means either that God is non-temporal or timeless, or that God has no beginning and no end. The first ('classical') view is found in Anselm, Augustine, Boethius, Aquinas, Calvin and Descartes.
Gist of Idea
God is 'eternal' either by being non-temporal, or by enduring forever
Source
Brian Davies (Introduction to the Philosophy of Religion [1982], 8 'Meaning')
Book Reference
Davies,Brian: 'An Introduction to the Philosophy of Religion' [OUP 1993], p.141
A Reaction
A God who is outside of time but performs actions is a bit of a puzzle. It seems that Augustine started the idea of a timeless God.