Laravel 5.1访客计数器不计入正确的访问次数

Question

I have a self-made visitor counter (sort of) I'm using the pragmarx plugin, but getting the data by myself.

So I have a chart, wich looks like this:

When I count everything from the day, there is no problem, it returns the correct values. But when I try to get the count of visits of each week, month or year, it returns the totally wrong numbers.

This is how I get my chart:

public function getVisitors()
    {
        $begin = Carbon::now()->startOfMonth();
        $end = Carbon::now()->endOfMonth();

        $stats = DB::table('tracker_sessions')
            ->whereRaw("created_at between '$begin' and '$end'")
            ->where('is_robot', '=', 0)
            ->groupBy(DB::raw('DATE_FORMAT(created_at,"%d-%m-%Y")'))
            ->orderBy(DB::raw('DATE_FORMAT(created_at,"%d-%m-%Y")'))
            ->get([
            DB::raw('DATE_FORMAT(created_at,"%d-%m-%Y") as y'),
            DB::raw('COUNT(DISTINCT client_ip) as b')
          ]
        );

          return $stats;
    }

And this is how I get everything by week:

public static function getVisitorsThisWeek()
    {
        $begin = Carbon::now()->startOfWeek();
        $end = Carbon::now()->endOfWeek();

        $stats = DB::table('tracker_sessions')
            ->whereRaw("created_at between '$begin' and '$end'")
            ->where('is_robot', '=', 0)
            ->count(DB::raw('DISTINCT client_ip'));

        return $stats;
    }

I'm doing the same for the month and the year, except then I change the Carbon::now()->startOfWeek(); to the Year or Month type of Carbon.

I really don't know what I'm doing wrong right now? I already tried to add the groupBy and orderBy, or switch them and so on, but noting seems to work. Hopefully someone can help me out with this.