DateTimeFormatConstraint.php

<?php

namespace Drupal\datetime\Plugin\Validation\Constraint;

use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\Core\Validation\Attribute\Constraint;
use Symfony\Component\Validator\Attribute\HasNamedArguments;
use Symfony\Component\Validator\Constraint as SymfonyConstraint;

/**
 * Validation constraint for DateTime items to ensure the format is correct.
 */
class DateTimeFormatConstraint extends SymfonyConstraint {
  public function __construct(mixed $options = NULL, public $badType = "The datetime value must be a string.", public $badFormat = "The datetime value '@value' is invalid for the format '@format'", public $badValue = "The datetime value '@value' did not parse properly for the format '@format'", ?array $groups = NULL, mixed $payload = NULL) {
    parent::__construct($options, $groups, $payload);
  }

}