static int EntryToGroupKey(CloudLogEntry entry)
 {
     var date = entry.DateTimeUtc.Date;
     return (date.Year * 100 + date.Month) * 100 + date.Day;
 }
 static string EntryToToken(CloudLogEntry entry)
 {
     return entry.DateTimeUtc.ToString("yyyyMMddHHmmssffff");
 }