Funnily enough I was testing out for game time late last night, I've found it possible to change the time by searching for larger values. Eventually this brings about 5 results which all seem to increase as time goes up. From what I could tell it splits each half up and one of the values resets at half time to 0 ready for the next half. If I remember correctly the value would go to 180 (45 mins 3 min each half).
What I then did was change the value that resets to 0 to 180 and that would then change the time to 45 mins, second half I did the same and then the game completed and went to the main menu. The only issue I had was when trying this on ultimate team, when I changed the time it would change without any issues, when the game completes it comes up with the score and the reward that you get, it would stop just before this screen then pop up the error message saying that it has lost connection and then exit the game meaning the game was not counted. With that I decided to keep the 5 results that I had earlier and play a match in ultimate team to see if there were any other values or if something else happened. I then found the same 5 values and played a whole match whilst watching them and changed them to the same values for half time and full time in the next game I played. Unfortunately this gave me the same error =(
My guess is that there is some other value where it will link it to a match to make sure the full game has been completed. If perhaps we can find that value and then change it maybe things will work.