Last year I could not do the foreign earned income exclusion because I moved out of the US in Aug 2016. Should I refile my 2016 taxes or can I use the credit this year?

Should I (or can I?) refile/adjust  my 2016 taxes because I moved out of the US in August 2016 & did not qualify for the foreign income exclusion taxes last year. Or can I get the credit for 2017? I will move back to US in June 2018 and have been out of the country over 330 days for 2017