10 am central standard time is 8 am for folks on the West Coast, so for all practical purposes the entry period ended on the 17th. 
As I recall I  made a quick visit to the contest page when I first saw it to see if it required any special items to be used. But obviously I wasn't looking for info about when the entry period ended. 

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I've gotten worked over by companies whose "the contest ends the 21st" meaning 12:01 am (which by the way is how your car insurance usually works). 

But since I was accustomed to being able to get the days specials up through midnite CST -- I admit I assumed July 18th was July 18....