<reponame> pushed:>2019-10-01but I don't get any results, although there were some commits in October.
One additional wrinkle is that search only works on the default branch. So if the repository you're looking for has only had activity on non-default branches, then it wouldn't show up in the search results. But if you search for only the repository itself, then you could iterate across the branches in each of them and see what the latest commit was on each.
Let us know if you have more questions.