public static DateHelper::dayOfWeekName($date = NULL, $abbr = TRUE)

public static DateHelper::weekDaysAbbr($required = FALSE)

public Datetime::getInfo() Returns

public static DateHelper::monthNames($required = FALSE)

public static Datetime::validateDatetime(&$element, FormStateInterface

public DateFormatter::formatTimeDiffUntil($timestamp, $options = array())

public DateTimeComputed::getValue($langcode = NULL)

public DateFormatInterface::isLocked()