How can PHP developers troubleshoot datetime display issues, such as consistently getting "01.01.1970" as the output, when using date formatting functions?

One common issue with datetime display in PHP is getting "01.01.1970" as the output, which typically indicates that the datetime value being used is invalid or not set correctly. To troubleshoot this issue, developers should check the input datetime value, ensure it is in the correct format, and consider using functions like strtotime() to convert the datetime value to a Unix timestamp before formatting it with date().

// Example code snippet to troubleshoot datetime display issues
$datetime = "2021-09-15 14:30:00"; // Input datetime value
$timestamp = strtotime($datetime); // Convert datetime to Unix timestamp

if ($timestamp === false) {
    echo "Invalid datetime format"; // Handle invalid datetime format
} else {
    $formatted_date = date("d.m.Y", $timestamp); // Format the Unix timestamp
    echo $formatted_date; // Output the formatted date
}