musical_era.rb

class Range
  def overlap(other)
    [self.begin, other.begin].max .. [self.end, other.end].min
  end
end

def musical_era_alive_in(start_life, end_life)
  [
    ['Medieval',    476..1400],
    ['Renaissance', 1400..1600],
    ['Baroque',     1600..1760],
    ['Classical',   1730..1820],
    ['Romantic',    1815..1910],
    ['Modern',      1900..2100]
  ].max_by { |_, r| r.overlap(start_life..end_life).size }.first
end

puts musical_era_alive_in(1800, 1950) # Romantic