What parameters can be used with mktime to specify whether it is daylight saving time or standard time?

To specify whether mktime should consider daylight saving time or standard time, you can use the "is_dst" parameter. This parameter allows you to indicate whether daylight saving time is in effect (1), not in effect (0), or let PHP determine it automatically (-1).

// Example usage of mktime with is_dst parameter
$timestamp = mktime(0, 0, 0, 3, 14, 2021, -1); // Automatically determine if daylight saving time is in effect
echo date("Y-m-d H:i:s", $timestamp);