Week Start day and View by Day calendar error

Hi again,

if you set in Admin CP the Week Star on Monday, the "View by Day calendar" gets an error that doesn't happen when you select on Sunday.

At the bottom of the calendar, in the clearer numbers of April (that belong to first week of May) the calendar shows an extra day (the 7th of May).

Pic related:

https://s9.postimg.cc/idkxh3een/extraday.png