What are some common mistakes that developers make when working with time-related functions in PHP and how can they be avoided to ensure accurate results?

One common mistake developers make when working with time-related functions in PHP is not setting the correct timezone. This can lead to inaccurate results when working with dates and times. To avoid this issue, always set the timezone explicitly at the beginning of your script using the `date_default_timezone_set()` function.

// Set the timezone to your desired value
date_default_timezone_set('America/New_York');