Mathematical calculations suggest that it is on this day that <a href="https://en.wikipedia.org/wiki/Dwarf_planet" id="mwWw" rel="mw:WikiLink" title="Dwarf planet">dwarf planet</a> <a href="https://en.wikipedia.org/wiki/Pluto" id="mwXA" rel="mw:WikiLink" title="Pluto">Pluto</a> moved inside the orbit of <a href="https://en.wikipedia.org/wiki/Neptune" id="mwXQ" rel="mw:WikiLink" title="Neptune">Neptune</a> for the last time before 1979.