Schedule rules expressions, compare dates

I want to be able to iterate through all issues created the previous day but I don't know how to compare dates. I was thinking I could do something like this but I am getting warning/errors in Workflow editor.

schedule rule Find all issues created today 
 
daily at 01:00:00 [issue.created > now - 86400] { 
  var user = null; 
  if (issue.Assignee == null) { 
    <define statements> 
  } 
}

Can somebody please point me in the right direction as to how I might achieve this?