Linux Mint 17.3 KDE updated. KDE 4.14.2

In System Settings > Date & Time tab Date & Time
When I select "Set date & time automatically" and select any server, I get the message "Unable to contact time server: Public Time Server (pool,ntp.org).", with the error message matching the sever I selected.

Is there a workaround to use a publice time server for adjusting date and time?
Note: My time zone setting is "Asia/Tokyo JCST"