How many days can I go downstairs on a sunny day?

The seventh day.

For those infected with home isolation and rehabilitation, home isolation must be completed for 7 days from the date of symptoms; If the fever symptoms subside for more than 24 hours, and other symptoms improve after 7 days of home isolation without taking antipyretics, the isolation can be lifted; If you still have fever symptoms, release the isolation after the fever symptoms subside for more than 24 hours and other symptoms improve.