The new STEM F-1 OPT extension allows a 24-month period of temporary training that directly relates to an F-1 student’s program of study in an approved STEM field. This 24 month extension replaces the 17-month STEM OPT extension. The 17-month STEM OPT regulations will stay in effect until May 9, 2016. The 24-month extension takes effect on May 10, 2016.