How can PHP developers ensure they are using the correct format for date and time functions to avoid errors in calendar week calculations?

When working with date and time functions in PHP, it's crucial to use the correct format to avoid errors in calendar week calculations. One common mistake is using the wrong format specifier, which can lead to inaccurate results. To ensure accuracy, developers should use the 'W' format specifier for calculating the calendar week based on ISO-8601 standards.

// Ensure correct format for calendar week calculations
$date = '2022-01-01';
$week = date('W', strtotime($date));
echo "Calendar week for $date is: $week";