At the beginning, God told Adam if he chose to eat the fruit of the forbidden tree, in the day he did that, he would die. However Adam didn’t die immediately. Now there are a couple ways to look at this. God could’ve just meant, spiritually speaking, Adam would be dead because Adam sinned and sin would enter him and the world. Adam would’ve chosen the wrong master to follow, and he would’ve been separated from God at that point – a spiritual death.
However, there is another possibility. What if God was speaking prophetically? Adam lived 930 years. If God meant a prophetic, 1000 yearlong day, as part of a cosmic 7000-year week, then Adam did die in that first day – the first 1000 years of Earth’s history.
But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.
Genesis 2:17
And all the days that Adam lived were nine hundred and thirty years: and he died.
Genesis 5:5
There are a few verses in the Bible that seem to indicate the latter – that there are indeed 1000-year prophetic days and that the Earth is on a grand prophetic week, or 7000-day timeline:
For a thousand years in thy sight are but as yesterday when it is past, and as a watch in the night.
Psalm 90:4
But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day.
2 Peter 3:8
He shall deliver thee in six troubles: yea, in seven there shall no evil touch thee.
Job 5:19