Ok just as dmertz said in above comment, "This must be reported on the tax return for the year in which the distribution occurred"
The reason you are getting the questions about distributions is the Saver's Credit. If you took money out, in prior years it can disqualify you.
Getting back to the main area, however, the date of the 1099R does not matter, if it is a 2018 1099R report on 2018 return, if it is a 2017 1099R report on the 2017 return.
