How can PHP be used to determine the start and end dates of daylight saving time?

To determine the start and end dates of daylight saving time in PHP, you can use the `date()` function along with the `strtotime()` function to calculate the dates based on the current year. By using the `date()` function with the "I" format parameter, you can check if daylight saving time is in effect. Then, you can calculate the start and end dates by adding or subtracting the number of seconds in a day multiplied by the number of days from the current date.

$currentYear = date('Y');
$dstStart = strtotime('second Sunday March ' . $currentYear . ' 02:00:00');
$dstEnd = strtotime('first Sunday November ' . $currentYear . ' 02:00:00');

echo "Daylight Saving Time starts on: " . date('Y-m-d H:i:s', $dstStart) . "<br>";
echo "Daylight Saving Time ends on: " . date('Y-m-d H:i:s', $dstEnd);