def date_key(cls, month_string):
		"""
		Return a key suitable for sorting by month.

		>>> k1 = ChannelPage.date_key('September, 2012')
		>>> k2 = ChannelPage.date_key('August, 2013')
		>>> k2 > k1
		True
		"""
		month, year = month_string.split(',')
		month_ord = cls.month_ordinal[month]
		return year, month_ord
Return a key suitable for sorting by month.

		>>> k1 = ChannelPage.date_key('September, 2012')
		>>> k2 = ChannelPage.date_key('August, 2013')
		>>> k2 > k1
		True