August 22, the date picker is first opened the dates are grey'd as appropriate.

Choose September.
The date picker will grey Wednesday through Friday on the first row as expected. However, Saturday 29th and Sunday 30th are still grey from the previous month, it doesn't "un-grey".

Go back to August, Wednesday 1st through Friday 3rd are still grey, when they should be black.

Browsing through more months will cause more dates to become grey but they never become black again.