NullableDate.php

<?php

trait NullableDate
{
    /**
     * Transform the date for display, add timezone if available
     *
     * @param string $field_name
     *
     * @param string $format
     *
     * @param string $tz
     *
     * @return \Carbon\Carbon
     */
    public function displayDate(string $field_name, string $format = 'j M Y h:i a', string $tz = null)
    {
        $field = $this->{$field_name};
        
        if (is_null($field)) {
            return null;
        }
        
        if (! $field instanceof Carbon) {
            $field = parent::asDateTime($field);
        }
        
        if ($field->lt(Carbon::parse('1000-01-01'))) {
            return null;
        }
        
        // If the user is logged in, get their timezone
        if (is_null($tz) && isLoggedIn() && me()) {
            $tz = me()->getTimezone();
        }
        
        Carbon::setToStringFormat($format);
        
        if ($tz && $tz != 'UTC') {
            return $field->setTimezone($tz);
        }
        
        return $field;
    }
}