Description:
------------
Since PHP 7.2.0 constants that where defined in DateTime moved to DateTimeInterface, see FR #71520 and PHP 7.2.0 ChangeLog:

$ php -r "echo PHP_VERSION;"
7.2.4

$ php -r "ReflectionClass::export('DateTimeInterface');"
Interface [ <internal:date> interface DateTimeInterface ] {

  - Constants [13] {
    Constant [ public string ATOM ] { Y-m-d\TH:i:sP }
    Constant [ public string COOKIE ] { l, d-M-Y H:i:s T }
    Constant [ public string ISO8601 ] { Y-m-d\TH:i:sO }
    Constant [ public string RFC822 ] { D, d M y H:i:s O }
    Constant [ public string RFC850 ] { l, d-M-y H:i:s T }
    Constant [ public string RFC1036 ] { D, d M y H:i:s O }
    Constant [ public string RFC1123 ] { D, d M Y H:i:s O }
    Constant [ public string RFC7231 ] { D, d M Y H:i:s \G\M\T }
    Constant [ public string RFC2822 ] { D, d M Y H:i:s O }
    Constant [ public string RFC3339 ] { Y-m-d\TH:i:sP }
    Constant [ public string RFC3339_EXTENDED ] { Y-m-d\TH:i:s.vP }
    Constant [ public string RSS ] { D, d M Y H:i:s O }
    Constant [ public string W3C ] { Y-m-d\TH:i:sP }
  }
...