God was, God is, and God will always be.

God was.  The God we serve today is the same God who spoke to Moses, the same God who tenderly breathed life into Adam.
But is that what it means when we say "God was?"

I think it means just that...He is the God of Moses and Adam and everything and everyone that has lived in the past.  And we serve that very same God.  But also I think it can mean so much more. 

God's reign spans over yesterday, today and tomorrow.  God reigned, past tense, over yesterday, true.  But He still reigns over yesterday.  Present tense, still reigning over what already happened.  The sins we have committed, have been paid for.  We do not have to pay for them if we believe in His ultimate sacrifice, sending His only son Jesus Christ to pay for them.  And God knows the sins we will commit tomorrow.  And they have already been paid for!  Praise the Lord they have already been paid for!

I think it allows us to view the past and what has happened in a victorious light and to understand that time is not to God what it is to us.  That He can still reign over something that has happened is almost impossible to understand.  And that is the beauty behind the so many mysterious of God.  And helps us understand that He reigns over today because He's already been here.  He's omnipotent in that He's everywhere, but He's also everywhere in the concept of time.  Reigning over the very beginning of "time" and the very end of "time."

And that gives me a sense of peace that cannot be shaken

"For I know the plans I have for you," declares the Lord, "plans to prosper you and not to harm you, plans to give you hope and a future.  Then you will call upon me and come and pray to me and I will listen to you.  You will seek me and find me when you seek me with all your heart."

Jeremiah 29:11 and 12

Come, let us seek the One who already knows.