If photons took 2 Earth's days to reach the Earth, they started travel at
d = c * t = 299792458 m/s * 2 * 24 * 3600s = 51,804,136,742,400 m = ~ 51800 millions km = ~51.8 billions km away from the Earth..
Each planet have different meaning/length of "day".
Prediction, observation and measurement of speed of light being finite, predates Einstein by centuries. Jupiter and Saturn have moons, which orbit around them. If you make measurements when the Earth is the closest to Jupiter or Saturn, and repeat measurement half-year later when Earth is on the opposite side of orbit, and the farthest from them, there is visible difference in delay that early astronomers noticed. In the case of Jupiter ~16 minutes. Why? Because the Earth is 300 millions kilometers away (in frame of reference of Solar System). Conclusion of astronomers: speed of light must be finite!