public DateFormatInterface::setPattern($pattern)

public DateFormatter::getSampleDateFormats($langcode = NULL, $timestamp

public DateFormatter::formatInterval($interval, $granularity = 2, $langcode

public static Datelist::processDatelist(&$element, FormStateInterface

public static Datetime::formatExample($format)

The human-readable name of the date format entity. Type: string File

protected DateFormatter::dateFormat($format, $langcode)

public DateFormat::isLocked() Determines

protected DateTimePlus::prepareTimezone($timezone)

public static DateTimePlus::arrayToISO($array, $force_valid_date = FALSE)