var successfulSessionsToday = //sum of all timeValues of sessions created today with success == true
var unsuccessfulSessionsToday = //sum of all timeValues of sessions created today with success == false

var successfulSessionAllTime = //sum of all timeValues of all sessions with success == true
var successfulSessionAllTime = //sum of all timeValues of all sessions with success == false

let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Sessions")

        do  {
            let results = try context.fetch(request) as! [NSManagedObject]

            if results.count > 0    {
                for result in results   {
                    if let startDate = result.value(forKey: "startDate")    {
                        print(startDate)
                    }
                    if let timeValue = result.value(forKey: "timeValue")    {
                        print(timeValue)
                    }
                    if let success = result.value(forKey: "success")    {
                        print(success)
                    }
                }
            }
        }   catch
        {
            // Error handling here
        }