What are some potential pitfalls when working with date and time functions in PHP?

One potential pitfall when working with date and time functions in PHP is not properly handling time zones. It's important to set the correct time zone to ensure accurate date and time calculations. To solve this issue, you can use the `date_default_timezone_set()` function to set the desired time zone.

// Set the default time zone to UTC
date_default_timezone_set('UTC');