I have a 2001, but manufactured in 2000, when should I replace the timing belt?

LOL Just kidding! (i knew day one I had a timing chain)

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2001 Ranger Edge 4x4 (sold)
2006 F150 Lariat 4x4 (sold)
2007 Explorer XLT (Destroyed by Deer on highway)
2014 Explorer XLT (inherited from parents)