It was under construction in Sep 2011 so was probably done by mid 2012. Link below http://www.pv-tech.org/chip_shots_blog/first_solar_mesa_construction_site_photo_blog_the_next_big_pv_production_fa Looks like Apple bought it in Nov 2013. Link below http://www.usatoday.com/story/money/business/2013/11/05/apple-plant-arizona/3440009/ http://cleantechnica.com/2013/11/29/apple-buys-first-solar-arizona-manufacturing-facility/ So ...three years is a reasonable guess.