Doesn’t the count of the Jubilee years use a solar calendar?

Answer: Yes.  Years are always counted according to the solar orbit.  The Jubilee was 49 years plus one equaling the 50 year Jubilee cycle.  These were solar years which were made up of 12 or 13 lunations.  This is why true calendation is a combination: luni-solar.  Twelve lunations are always 11 days short of a solar year.  Every two to three years, an extra lunation is added in as a “leap month” to bring the lunations back into alignment with the seasons according to the solar year.