https://bugs.php.net/bug.php?id=77741&edit=2
PHP :: Bug #77741 :: DateTimeZone/setTimezone returns wrong values
phpbugreturnswrongvalues
https://www.php.net/manual/zh/intlcalendar.settimezone.php
PHP: IntlCalendar::setTimeZone - Manual
Set the timezone used by this calendar
phpmanual
https://bugs.php.net/bug.php?id=61483&edit=1
PHP :: Bug #61483 :: When overriding DateTime::setTimezone() no type hint can be added.
https://www.php.net/manual/en/datetime.settimezone.php
PHP: DateTime::setTimezone - Manual
Sets the time zone for the DateTime object
phpdatetimemanual
https://api.drupal.org/api/drupal/core%21modules%21datetime%21src%21Plugin%21Field%21FieldFormatter%21DateTimeFormatterBase.php/function/DateTimeFormatterBase%3A%3AsetTimeZone/9
function DateTimeFormatterBase::setTimeZone | Drupal API
functiondrupalapi