When were the most recent publications of pre-training data included?

I know that SciBERT is pre-trained by the Semantic Scholar corpus. I also know that the Semantic Scholar corpus is not publicly available.

I am wondering how many new papers are included in the pre-training data. For example, **are papers from ACL 2018 included?**
The Semantic Scholar Corpus paper was published in 2018 or so, so I'm guessing that's right around the borderline between having a paper...