Re-index a php array on key

I have an array created in PHP which is used downstream in a Garmin connectIQ app. I have created a script which generates the below Var_export

  array (
  '2022-05-14' => 
  array (
    0 => 
    array (
      'index' => 0,
      'time' => '05:18:31',
      'timeE' => 1652501911,
      'type' => 'High',
      'height' => '7.9m',
      'diff' => '1day 15hrs',
    ),
    1 => 
    array (
      'index' => 1,
      'time' => '11:39:16',
      'timeE' => 1652524756,
      'type' => 'Low',
      'height' => '1.3m',
      'diff' => '1day 8hrs',
    ),
    2 => 
    array (
      'index' => 2,
      'time' => '17:43:49',
      'timeE' => 1652546629,
      'type' => 'High',
      'height' => '8m',
      'diff' => '1day 2hrs',
    ),
    3 => 
    array (
      'index' => 3,
      'time' => '23:57:31',
      'timeE' => 1652569051,
      'type' => 'Low',
      'height' => '1.2m',
      'diff' => '20hrs 27mins',
    ),
  ),
  '2022-05-15' => 
  array (
    4 => 
    array (
      'index' => 4,
      'time' => '06:02:02',
      'timeE' => 1652590922,
      'type' => 'High',
      'height' => '8.3m',
      'diff' => '14hrs 22mins',
    ),
    5 => 
    array (
      'index' => 5,
      'time' => '12:22:53',
      'timeE' => 1652613773,
      'type' => 'Low',
      'height' => '1m',
      'diff' => '8hrs 2mins',
    ),
    6 => 
    array (
      'index' => 6,
      'time' => '18:26:19',
      'timeE' => 1652635579,
      'type' => 'High',
      'height' => '8.4m',
      'diff' => '1hr 58mins',
    ),
  ),
)

However, what I need, is the output to be re-indexed on each date change

array (
      '2022-05-14' => 
      array (
        0 => 
        array (
          'index' => 0,
          'time' => '05:18:31',
          'timeE' => 1652501911,
          'type' => 'High',
          'height' => '7.9m',
          'diff' => '1day 15hrs',
        ),
        1 => 
        array (
          'index' => 1,
          'time' => '11:39:16',
          'timeE' => 1652524756,
          'type' => 'Low',
          'height' => '1.3m',
          'diff' => '1day 8hrs',
        ),
        2 => 
        array (
          'index' => 2,
          'time' => '17:43:49',
          'timeE' => 1652546629,
          'type' => 'High',
          'height' => '8m',
          'diff' => '1day 2hrs',
        ),
        3 => 
        array (
          'index' => 3,
          'time' => '23:57:31',
          'timeE' => 1652569051,
          'type' => 'Low',
          'height' => '1.2m',
          'diff' => '20hrs 27mins',
        ),
      ),
      '2022-05-15' => 
      array (
        0 => 
        array (
          'index' => 4,
          'time' => '06:02:02',
          'timeE' => 1652590922,
          'type' => 'High',
          'height' => '8.3m',
          'diff' => '14hrs 22mins',
        ),
        1 => 
        array (
          'index' => 5,
          'time' => '12:22:53',
          'timeE' => 1652613773,
          'type' => 'Low',
          'height' => '1m',
          'diff' => '8hrs 2mins',
        ),
        2 => 
        array (
          'index' => 6,
          'time' => '18:26:19',
          'timeE' => 1652635579,
          'type' => 'High',
          'height' => '8.4m',
          'diff' => '1hr 58mins',
        ),
      ),
    )

I have been unable to figure this one out and my searches are coming up short. Appreciate any guidance offered