code: def plot(hdiff, title):
      
      import matplotlib.pyplot as plt
      years = [elem[0] for elem in hdiff]
      diffs = [elem[1] for elem in hdiff]
      plt.plot(years, diffs)
      plt.ylabel('Distance in minutes')
      plt.xlabel('Year')
      plt.title(title)
      plt.axhline(y=0, c='red')
      plt.show()
docs: Plots the tropical solar length
      by year.