Alpha and Omega means eternity past and future.
No beginning and no end.

The explanation of creation in the Bible is not very specific...
It doesn't have to be.
The point is, God created the vastness of this universe for Mankind.

Even if you could understand it, you still wouldn't possess the mind of GOD.
The nature of God's creation is our limitation.
We are just a spec of dust in this universe...
And, this universe is just a snow-globe on God's desk.

We count the days and years of our lives by how many times this spec of dust rotates around a sun. When exactly did we begin counting those rotations? Roughly 6000yrs ago.

Here's the real question; If you are the Alpha and Omega creating a universe, then what defines a day of God's time in eternity?

So...
"When did God create the Earth?"
Answer;
Right on time. "And it was good"