If you run a realistic physical simulation of a star, and you include every subatomic particle in it, you’re going to have to use very small time increments. Computers can’t handle anywhere near that many particles yet, but mark my words, physicists of the future are going want to run this simulation as soon as we have the computer to do it. Also, the simulation should predict events billions of years in the future, so you may need to build a new time tracking system to handle that.