How far in advance do I need to renew a passport in order to travel?

My passport expires on May 3rd of this year, so obviously I have to renew it before I travel to England at the end of May. However, I may also be traveling

Source: http://www.us-passport-service-guide.com/how-far-in-advance-do-i-need-to-renew-a-passport-in-order-to-travel.html

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