I was poking about trying to find where the "endgame date" (2050) is. I haven't spotted it yet. In previous games, you could edit your config so that your game could go beyond that set date (basically you set it to something else).
You shouldn't need to edit any Config files, just turn off the Time Victory option from the "Select Victories" section of the main "Set Up Game" menu when you're starting. Then the game won't stop until someone reaches one of the other four victory conditions.