How can PHP developers ensure their applications are future-proof when setting cookie expiration dates without relying on UNIX timestamps?

To ensure that PHP applications are future-proof when setting cookie expiration dates without relying on UNIX timestamps, developers can use the `time()` function in combination with a specific date format. By converting the desired expiration date to a UNIX timestamp using `strtotime()`, developers can set the cookie expiration date accurately without relying on UNIX timestamps directly.

// Set cookie expiration date to 1 week from the current time
$expiration_date = strtotime('+1 week');
setcookie('cookie_name', 'cookie_value', $expiration_date, '/');