God is eternal. As created beings, we have a tendency to misunderstand the full scope of what it means to be eternal. We are prone to define what it means to be eternal in regards to a time line. One of the wrong ways of stating it is, something is eternal if it is always going to exist. Or if there will never come a day when it ceases to exist.
We might differentiate the eternality of man, which is eternal into the future, from the eternality of God, which is eternal both into the past and into the future. But this is a false construct, a misunderstanding of both eternality and God.
God cannot be measured in time, He created it just like He created space. Space He filled up with matter, and time He filled up with events. He is omnipresent within space, and in the same way He is omnipresent in time. God is not eternal because He exists eternally in both directions, past and future, but rather because He is Lord over time.
Time is not even eternal in both directions, past and future. Time has a beginning. Time only goes backward to the point where God created it. But God existed outside of the realm of time He created. He is eternal because He exists outside of time. So just like God is omnipresent in space, meaning that He is equally present in all places, He is also omnipresent in time, meaning He is simultaneously in all times. He sees your birth and your death at the same time. He is currently in the now, but He is also currently in every other time. We move through time. He is Lord over time.
Because of this I think it would be better if we never described anything created as eternal. God is eternal, meaning He is Creator of and Lord over time. Everything else is either temporary or everlasting. Something which is everlasting, has a starting point but does not have an ending point. Human beings are everlasting, but only God is eternal.