Add a twig filter to check if a date range is all day

src/Twig/Extension/SmartDateExtension.php

+<?php
+
+namespace Drupal\smart_date\Twig\Extension;
+
+use Drupal\smart_date\SmartDateTrait;
+use Twig\Extension\AbstractExtension;
+use Twig\TwigFunction;
+
+/**
+ * Twig Extension class for Smart Date.
+ */
+class SmartDateExtension extends AbstractExtension {
+
+  /**
+   * {@inheritDoc}
+   */
+  public function getFunctions() {
+    return [
+      new TwigFunction('is_all_day', [$this, 'smartDateIsAllDay']),
+    ];
+  }
+
+  /**
+   * Evaluates whether or not a provided range is "all day".
+   *
+   * @param object $start_ts
+   *   A timestamp.
+   * @param object $end_ts
+   *   A timestamp.
+   * @param string|null $timezone
+   *   An optional timezone override.
+   *
+   * @return bool
+   *   Whether or not the timestamps are considered all day by Smart Date.
+   */
+  public function smartDateIsAllDay($start_ts, $end_ts, $timezone = NULL) {
+    return SmartDateTrait::isAllDay($start_ts, $end_ts, $timezone);
+  }
+
+}