def test_periodIntersect_whenPartiallyOverlap(self) :
		p1 = Period("2013-01-01","2015-03-20")
		p2 = Period("2015-01-01","2016-03-20")
		self.assertEqual(
			p1.intersect(p2).t,
			("2015-01-01","2015-03-20"))
	def test_periodIntersect_whenDifers(self) :
		p1 = Period("2013-01-01","2014-03-20")
		p2 = Period("2015-01-01","2016-03-20")
		self.assertEqual(
			p1.intersect(p2).t,
			("2015-01-01","2014-03-20"))