The cluster hosting
time1.google.com went down for routine maintenance. The redirect of
time.google.com was changed to ensure that devices that can only have one peer still got service. If you can use more than one peer (i.e. you have a regular ntpd installation) then use all four of time1..
time4.google.com and the client will be robust to service maintenance like this, as recommended in the service docs:
https://developers.google.com/time/guides
time1 will be back on its feet once the maintenance window is over.
Aside, at the moment we're working on some improvements to avoid this sort of maintenance being visible to you entirely.