Google's SLA will no longer have an "out" for planned downtime. Customers will receive SLA credits for any downtime - planned or unplanned. Google claims to be the first major cloud provider to eliminate maintenance windows from its service level agreement.
Previously, Google did not count periods shorter than 10 minutes as downtime. That meant that even though short outages could add up to hours over a long enough period of time, the company had no obligation to compensate users. Google is ending that policy and will now credit users for any amount downtime, no matter how brief.