如何在日期差异功能中使用变量？

I am using an ACF Field to allow a client to content manage a countdown to their next event I am using JS flip clock on the desktop version but as it isn't responsive, I decided to use date diff to echo out just the number of days for mobile.

The site is currently live at theindustrialproject.co.uk

The code I currently have is this:

<?php
    $date1 = date_create(date());
    $date2 = date_create(the_field('mobile_date'));
    $diff = date_diff($date1,$date2);

    $difference = $diff;

    if ($difference < 0) { $difference = 0; }
    echo '<span class="countdown-mobile">'. floor($difference/60/60/24)."</span><br />";
    if ($difference == 1) { echo "<p>Day</p>"; }
        else { echo "<p>Days</p>"; }
?>

but it always returns 0. For reference, I pulled the code from here

Without knowing what the function the_field('mobile_date') will return ( either a date or timestamp? ) you might need to alter that particular line below but you should be able to use the DateTime object and format the difference like this

$format='Y-m-d';
$timezone=new DateTimeZone('Europe/London');

/* We need 2 datetime objects - one for now the other for the future date */
$now=new DateTime( date( $format, strtotime('now') ), $timezone );
$target=new DateTime( the_field('mobile_date'), $timezone );

/* Format the difference in days */
$days = $now->diff( $target )->days;

echo "<span class='countdown-mobile'>{$days}</span><br />" . ( $days == 1 ? '<p>Day</p>' : '<p>Days</p>' );