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 22.214.171.124, a rather less pretty IP address than the 126.96.36.199 and 188.8.131.52 Google uses for its public domain-name system (DNS) servers.
There's also time2.google.com at 184.108.40.206, time3. at .8 and time4. at .12.