I get it - you're working backwards from the answer you want.
As a grad student I graded homework papers for students using a textbook with the answer ( question 14 = 1.68 m) in the back of the book. For some questions, the student had to assume a water temperature, usually 4C or 20C. at the beginning of the solution for properties of the water. If the temperature was different from the assumed temperature used by the book's author, the student's answer would be slightly off. Students would then start working backwards from the answer in the book but didn't change their assumptions at the beginning. From the initial assumption to the answer from the book required them to erase their correct work and make math errors somewhere in their solution.
You have your answer - biblical literalism. You are working backwards from the answer you want but you don't know how to work out the solution.
What is your evidence that time moves at different rates depending on location?
Do you have any concept of how that would look? What evidence you're looking for?