How do I apply date('H:i:s', $this_array)??

You should be able to use eloquent casting on your model to set the format to what you want

protected $casts = [
    'time' => 'datetime:H:i:s',
];

https://laravel.com/docs/5.8/eloquent-mutators#array-and-json-casting

@D9705996 - Thanks!!! I tried it but now my Y axis on my chart says "object object"

        $latestfeed72 = Feed72::orderBy('time', 'desc')->take(100)->get();
        $realtime_labels_array = $latestfeed72->pluck('time')->toArray();
        $realtime_data_array = $latestfeed72->pluck('data')->toArray();

        $realtime_consumption_chart = new ChartJS;
        $realtime_consumption_chart->labels($realtime_labels_array);
        $realtime_consumption_chart->dataset('My dataset', 'line', $realtime_data_array);

This is what the complete use is like..

the time column is in UNIX/EPOCH time. This is why I'm trying to convert it.

You need to ensure you are passing the data from your backend to you frontend in the format chart.js expects. Have a tinker with console.log in you front end to see what's going wrong

What is time? Is it a carbon object, a string? Is it only time, or a datetime?

Does this work for you?

$realtime_labels_array = $latestfeed72->pluck('time')->toArray();
$realtime_labels_array = array_map(function($t) { return date("H:i:s", strtotime($t)); }, realtime_labels_array);

@CRONIX - "time":1549169750000,"data":"23527"

@CRONIX - I tried this:

        $realtime_labels_array = array_map(function($t) { return date("H:i:s", strtotime($t)); }, $realtime_labels_array);

but it turned all my labels to zeros.

It would help to show the output of

$realtime_labels_array = $latestfeed72->pluck('time')->toArray();
dd($realtime_labels_array);

I was guessing because you didn't show what data you are actually working with.

$realtime_labels_array = array_map(function($item) {
    return [
        'time'=> date('H:i:s', strtotime($item['time'])),
        'data' => $item['data']
    ];
}, $times);

Maybe that will work, but I don't know if you're working with an array of arrays or an array of objects. If objects, you'd have to use object notation instead of array notation like I'm showing.

@CRONIX - This is what I've got:

array:100 [▼
  0 => 1552079470
  1 => 1552079460
  2 => 1552079450
  3 => 1552079440
  4 => 1552079430
  5 => 1552079420
  6 => 1552079410
  7 => 1552079400
  8 => 1552079390
  9 => 1552079380
  10 => 1552079370
  11 => 1552079360
  12 => 1552079350
  13 => 1552079340
  14 => 1552079330
  15 => 1552079320
  16 => 1552079310
  17 => 1552079300
  18 => 1552079290
  19 => 1552079280
  20 => 1552079270
  21 => 1552079260
  22 => 1552079250
  23 => 1552079240
  24 => 1552079230

This will convert the array you gave (using first 4 timestamps from your post) into the same array using H:i:s. I don't know if it's what you need for charts to work, but it should do what your original question asks according to my test shown below.

>>> $dates = [1552079470, 1552079460, 1552079450, 1552079440];
=> [
     1552079470,
     1552079460,
     1552079450,
     1552079440,
   ]

>>> $formattedDates = array_map(function($time) { return date("H:i:s", $time); }, $dates);
=> [
     "21:11:10",
     "21:11:00",
     "21:10:50",
     "21:10:40",
   ]

@CRONIX - Is there any way to change:

        $latestfeed72 = Feed72::orderBy('time', 'desc')->take(100)->get();

to only query the records in 10 minute intervals? Right now the database contains values at 10 sec intervals.

Maybe there is a skip() that will skip over and read only every 60th record?

Disregard: Just discovered:

$collection->nth(4);