How can the error message "It is not safe to rely on the system's timezone settings" be addressed in PHP code, and what impact does it have on the application?

To address the error message "It is not safe to rely on the system's timezone settings" in PHP, you can set the timezone explicitly in your code using the `date_default_timezone_set()` function. This ensures that your application has a consistent timezone setting regardless of the system settings.

// Set the timezone to UTC
date_default_timezone_set('UTC');