Cron: Don't use a tz other than the default one

src/Cron.php

@@ -5,6 +5,7 @@
 use Cron\CronExpression;
 use DateTime;
 use DateTimeInterface;
+use DateTimeZone;
 use InvalidArgumentException;
 use ipl\Scheduler\Contract\Frequency;
 
@@ -98,6 +99,9 @@ public function getExpression(): string
     public function startAt(DateTimeInterface $start): self
     {
         $this->start = clone $start;
+        // If the start time tz is somehow set to UTC (because someone didn't use our frequency format),
+        // but are using non UTC tz, we have to enforce to use the configured default time zone.
+        $this->start->setTimezone(new DateTimeZone(date_default_timezone_get()));
 
         return $this;
     }
@@ -112,6 +116,9 @@ public function startAt(DateTimeInterface $start): self
     public function endAt(DateTimeInterface $end): Frequency
     {
         $this->end = clone $end;
+        // If the end time tz is somehow set to UTC (because someone didn't use our frequency format),
+        // but are using non UTC tz, we have to enforce to use the configured default time zone.
+        $this->end->setTimezone(new DateTimeZone(date_default_timezone_get()));
 
         return $this;
     }