You may have noticed that most in-progress events are now showing 12 digit event IDs, like we’re used to.
What Leago is doing is if no section dates have been entered yet, they use the current date to generate a temporary event ID, which will change if the latest section ending date is something other than today.
Some older events may not have them yet, many of those are probably ones that need to be deleted by the person who generated them. (Some people have reported problems deleting their test events, if that happens to you , drop a note to ratings-support@uschess.org.)