About
You can use publicly available NTP server on ntp.cihar.com. It is also part of pool.ntp.org.
Server statistics are available at pool.ntp.org.
Usage
Preffered way of using this server is through pool.ntp.org, this will prevent you from possible outages of this server:
server 3.cz.pool.ntp.org server 3.europe.pool.ntp.org server 2.europe.pool.ntp.org