note: This is an "extended comment" type answer, addressing two potential solutions that may not be exactly what you need, but are close.
A thing which gives you positions of things in the solar system given a specified time is called an Ephemeris.
Originally they were tables of predictions (past and future) based on calculations. By the time of Newton, they became quite good, since Newton developed a method to iteratively solve Kepler's equation (e.g. Newton's Method). See the question How did Newton and Kepler (actually) do it? and the answers there for a little more background.
The Python package PyEphem has been around and well supported, and is the pythonic reincarnation of XEphem. I haven't used it, but I believe it keeps enough information about orbital parameters at certain epochs to generate an ephemeris, including some gravitational perturbations. In other words, it's much more than planets moving on fixed elliptical orbits around a fixed sun. So I believe it runs without internet connection.
I never used it because I was recommended to look at Skyfield and it's exactly what I needed. It downloads a standard JPL ephemeris that you choose, and then just uses it from your hard drive after that. However, in order to deal with leap seconds and other time related effects, it occasionally needs to check the internet for leap second information updates, since these are arbitrary.
I don't know if Skyfield has a mode to avoid that. Actually that's a good question. If you work with a timescale that doesn't have leap seconds, I am not sure if it will run in its current version.
Both Skyfield and PyEphem Python packages have been written and are maintained by @BrandonRhodes.
If you can allow an occasional connection to the internet (say every month or few months) then Skyfield is extremely easy and pythonic to use. For example here is a script I used in this answer. If you want to convert time formats from system time, you can search my questions in stackoverflow and space exploration. If you want it for your local computers system time now, you just use
t = ts.now() directly instead of utc.
import numpy as np
import matplotlib.pyplot as plt
from skyfield.api import load
data = load('de421.bsp')
ts = load.timescale()
t = ts.utc(2016, 7, 5, 9, 50, 0)
jupiter, earth = data['Jupiter barycenter'], data['Earth']
jpos, epos = jupiter.at(t).position.km, earth.at(t).position.km
d_instantaneous = np.sqrt(((jpos - epos)**2).sum())
d_light = earth.at(t).observe(jupiter).distance().km # where WAS Jupiter 48 minutes ago?
clight = 299792.458 # km/s
print "d_instantaneous / c = ", d_instantaneous/clight
print "d_light / c = ", d_light/clight