Get difference between two dates programatically

Question

In summary:

On a Drupal 8 project, i am trying to programatically get the difference between two different times (current time - Node creation time)

Use case:

I have "nodeabc" already available on the site.

When a specific webform is submitted and by using a custom webform handler, I want to get the difference in minutes between current time and nodeabc creation time.

Say nodeabc was created on: 24/06/2019 08:00 AM and the webform is being submitted on: 24/06/2019 07:00 PM, so the difference between both times will be: 660 minutes.

I have already loaded the node by its nid but how to continue in achieving the above ?

UPDATE #1:

From @Prestosaurus answer, I did the below in my webform custom handler php file:

$nid = '125';
$node = \Drupal\node\Entity\Node::load($nid);

$creationtime = $node->getCreatedTime();

// Get "Time Diff Since" creation time.
$creationsince = \Drupal::service('date.formatter')->formatTimeDiffSince($creationtime);

the above code returned: 7 hours 30 minutes which is good but then I added the below code to the above one:

$totalamount = $creationsince * 5000;

But while testing it returns a php error InvalidArgumentException: $string ("35000") must be a string.

I believe I am half way to the answer but still need to convert the $creationsince value to 450 minutes instead of 7 hours 30 minutes.

Is that doable ?

Answer 1

Given a node, $node:

$diffSeconds = time() - $node->getCreatedTime();
$diffHours = (($delta_seconds / 60.0) / 60.0);
$formattedTimeDiff = \Drupal::service('date.formatter')
  ->formatTimeDiffSince($node->getCreatedTime());

$diffSeconds is the number of seconds between node creation time and now.

Thus $diffHours is the number of hours (float) between node creation time and now.

formatTimeDiffSince() converts this to a human readable value, e.g. "1 hour 15 minutes"

---

For the webform timestamps:

function MYMODULE_preprocess_node(&$variables) {

  $createdTimestamp = $variables['node']->getCreatedTime();

  $webform_submissions = \Drupal::entityTypeManager()
    ->getStorage('webform_submission')
    ->loadByProperties([
    'entity_type' => 'node',
    'entity_id' => $variables['node']->id(),
  ]);

  $submission_timestamps = [];
  $timeDiffs = [];
  $timeAgos = [];

  foreach ($webform_submissions as $submission) {
    $submission_timestamps[] = $submission->completed->value;
    $timeDiffs[] = $submission->completed->value - $createdTimestamp;
    $timeAgos[] = \Drupal::service('date.formatter')
      ->formatTimeDiffSince($submission->completed->value);
  }

}

Webform timestamps cover ->created, ->completed, and ->changed.