"Time is relative and something which we have designed"
I do agree with the first part of your statement. Einstein himself has proven that Time is relative, so I doubt anyone can actually put those words in doubt.
However, any pretense of credibility you might have had falls flat on its face with the last part of your statement.
Nobody in the Human race has "designed" Time. If that were the case, we would have included methods to "wind back" Time and otherwise exert full control over it.
What the Human race has designed is its own understanding of time, yes. But Time will go on whether there is a human being to measure it or not.
I accept the idea that the Universe originated in the Big Bang - until a better scientific theory comes along. I accept the idea that immense and numerous stellar explosions were required to create the various kinds of matter that exist beyond the humble hydrogen atom. I accept that it probably took billions of years and untold trillions upon trillions of events to create the conditions that made life on this planet Earth possible.
And I also accept, and welcome, the idea that there is a God who, in His godly wisdom and intelligence, set the whole thing in motion and made sure to provide all the tools we needed to understand it.
The two items are not mutually exclusive, and I see no reason to consider that Science is diminishing God in any respect. On the contrary, I believe that Science simply demonstrates that God does indeed have a vastly superior intelligence to our own, and we should be in awe of what God has created and thankful to have the ability to take tiny steps in understanding it.
Because if we had designed the Universe, the specs would still be stuck in a committee and the beta version would have blue screened right after the first black hole.