article_snippet.sent: but I know that Bernard does not know too.
article_snippet.sent: Bernard might have been the number 18 or 19.
article_snippet.sent: For Albert to be 'certain' that Bernard doesn't know, Albert must have been given a month that does not contain one of these 'unique' dates - i.e. July or August.
article_snippet.sent: This is because Bernard realises Albert has ruled out May and June because of the 'single number' aspect above.
article_snippet.sent: However, as Bernard states that Bernard now knows the date, we can rule out July 14 or August 14.
article_snippet.sent: This means her birthday must be the only remaining date in the month Albert was originally told.