When you set up your timeOS account, remember to set up the sub-calendars you'd like to get reminders on.
Go to the new tab page.
Click on 'Preferences'
Click on 'Calendars'.
Toggle on and off the sub-calendars you'd like to get reminders and have a view on your new tab.
How do I subscribe to a calendar to see it on my sub-calendar?
Can I add more calendar accounts to my timeOS account?
Currently, timeOS doesn't support multiple accounts, but it's on our Roadmap.