The NTP pool project is participating in ... / 2011-06-07

The NTP pool project is participating in World IPv6 day. Well, not participating in the 'switching off after 24 hours' bit: 2.pool.ntp.org now has AAAA records and will keep them. In the current default configuration this means a system with broken IPv6 connectivity will still work, it will just decide one of the servers is unreachable and tick on happily.

koos@greenblatt:~$ host 2.pool.ntp.org
2.pool.ntp.org has address 213.249.66.35
2.pool.ntp.org has address 91.148.192.49
2.pool.ntp.org has address 72.26.217.210
2.pool.ntp.org has IPv6 address 2001:4f8:fff7:1::17
2.pool.ntp.org has IPv6 address 2607:f128:42:63::2
2.pool.ntp.org has IPv6 address 2600:3c00::2:b401

Source: Experimentally enabling IPv6 - NTP Pool News.

It's not possible to add ntp.cs.uu.nl to the ipv6 pool at the moment, but ntp.idefix.net is reachable via IPv6 and is ok as a server. So it is in the pool.