systemd should not default to using time{1,2,3,4}.google.com.

Google doesn't provide timeX.google.com as a public service(0). We don't maintain this to the same level of reliability/availability that we work hard to provide with other services (eg Google Public DNS, websearch etc). We use this for systems outside of our datacenters that need to understand our concept of time.

Google (famously(1)) runs a non standard concept of time, that works well if everything in your infrastructure knows and understands this and is designed to work with this. If you mix and match NTP servers within a machine you'll run into problems (since Google's timeservers are deliberately false ticking). If you mix and match between machines (eg some hosts use Google's time servers, and some use NIST timeservers) then your time won't match up between them. As I write this Google's clock is ≈-0.4s out from UTC.

Services such as NFS are likely to be confused as to the creation times of files and so on, logs won't be comparable between hosts etc.

People shouldn't be using these time servers for their own use. People should definitely /not/ be using these time servers by default without realising it.

Please change systemd's default time servers to some service that is designed to provide a reliable public NTP service.

(0): http://googlecloudplatform.blogspot.com/2015/05/Got-a-second-A-leap-second-that-is-Be-ready-for-June-30th.html
(1): http://googleblog.blogspot.com/2011/09/time-technology-and-leaping-seconds.html