We don't know that, and you did your math on an age of 13.7 billion years, not 17.3 billion years.
Both are widely accepted by separate scientific groups, showing how ridiculous it is to use either for a mathematical equation.
It could be 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000 years or one day. It's not relevant, as time is but a manmade concept.
You still have to prove god exists, which means you would have to prove who/what created him.
You think god created the universe. Right so far?
That would mean god is more intelligent and more complex than the universe. Right so far?
You think he has always existed. Right so far?
Ergo, it follows that if it's possible that god always existed, something simpler and less intelligent could have always existed.
Throw in the certainty that our universe does exist and the absolute dearth of evidence that god exists, and you recognize the futility of your premise.