You don't have to run a report right now — you can schedule it to generate later, with that future date's information.
1. Go to Reports & Imports › Request a Report and click Generate on the report you want.
2. Set the Date Range if the report uses one.
3. Under Generate, click Later and pick a date and time. It runs automatically then, in your site's timezone.
4. Click Request Report.
The report appears on Reports & Imports › Past/Scheduled Reports with a Scheduled status and the time it will run.
Cancel on that row calls the run off before it happens.
When its time comes it starts on its own. You'll see a progress bar while it generates, and once it finishes the status flips to Ready with a row count and a Download button — right there in the same list.