What are some common misunderstandings or misconceptions about date calculations in PHP, particularly when adding or subtracting months from a given date?

One common misunderstanding when adding or subtracting months from a date in PHP is that simply adding or subtracting 30 days may not always give the desired result due to varying month lengths. To accurately add or subtract months, it is recommended to use the `DateTime` class along with the `DateInterval` class to ensure proper handling of different month lengths and leap years.

$date = new DateTime('2022-03-15');
$date->modify('+1 month');
echo $date->format('Y-m-d');