“Israel declared independence on May 14, 1948 and neighboring Arab states attacked the next day.”

So it doesn’t look like Obama’s speech is scheduled for Israel’s Independence Day, it is however the day before the anniversary of the beginning of the Six Day War:
http://www.washingtontimes.com/news/2009/may/09/egypt-picked-as-stage-for-obama-talk-to-muslims-wi/
http://en.wikipedia.org/wiki/Six-Day_War

Here’s a conspiricy with the exactly correct date, though - Islam Day in Hawaii:
http://www.foxnews.com/politics/2009/05/06/hawaii-lawmakers-pass-create-islam-day/

September 24th is 9/11 in the old Julian calendar:
http://en.wikipedia.org/wiki/Julian_Calendar