https://www.theverge.com/2018/7/27/17621266/google-home-schedule-routines

Google Assistant introduced multi-step routines earlier this year, allowing for a combination of several actions (toggling lights, changing the thermostat, etc.) to be carried out with one command. At the time, it was said that Google was also planning to add the ability to schedule routines, but no timeframe was given except “later this summer.” Now, as Droid Life spotted on Reddit, it looks like the scheduling feature is rolling out.

As of yesterday, some users are seeing the option, which appears within the Google Home app. Tap Settings, then Routines, and then the “+” button to create a routine. If its available for you, there should also be an option to “Set a time and day (optional).”