system/I18n/Time.php
public function getDst(): bool
	{
		// grab the transactions that would affect today
		$start       = strtotime('-1 year', $this->getTimestamp());
		$end         = strtotime('+2 year', $start);
		$transitions = $this->timezone->getTransitions($start, $end);

		$daylightSaving = false;
		foreach ($transitions as $transition)
		{
			if ($transition['time'] > $this->format('U'))
			{
				$daylightSaving = (bool) $transition['isdst'] ?? $daylightSaving;
			}
		}
		return $daylightSaving;
	}
public function getDst(): bool
	{
		// grab the transactions that would affect today
		$start       = strtotime('-1 year', $this->getTimestamp());
		$end         = strtotime('+2 year', $start);
		$transitions = $this->timezone->getTransitions($start, $end);

		$daylightSaving = false;
		foreach ($transitions as $transition)
		{
			if ($transition['time'] > $this->format('U'))
			{
				$daylightSaving = (bool) $transition['isdst'] ?? $daylightSaving;
			}
		}
		return $daylightSaving;
	}
Are we in daylight savings time currently?

@return boolean