Google's turned on a set of public network time protocol (NTP) servers.
You'll find the servers at time.google.com – which resolves to 220.127.116.11, a rather less pretty IP address than the 18.104.22.168 and 22.214.171.124 Google uses for its public domain-name system (DNS) servers.
There's also time2.google.com at 126.96.36.199, time3. at .8 and time4. at .12.