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# Earth geopotential effect on orbit propagation

I'm trying to take into account the Earth geopotential effect on the orbit. The only term I could consider, is J2.

1. Are the terms (J2, etc.) change with time?
2. I found other terms coefficients here. How to add them also to differential equation, taken from here?

3.Why does the shown equation give 1 km error in 1 day in comparison with GMAT (configuration is below)? The coefficients for Eq radius and J2 are the same. The integrator is 9th order Runge-Kutta with tol=10e-13.