[Bug-16909]Date Picker: previous month ending day numbers are incorrect

Not 100% sure this is Maker specific, but when using a date picker in Perspective runtime on my phone and looking at August 2020, it shows the last few days of July, but incorrectly counts back from 30 instead of 31.

There appear to be more errors as well. The 1st of the month is always on the correct day of the week, but the end of the previous month is wrong. April 2020 shows February as the previous month (29 days). I’d have to look at it more, but I get the impression that maybe there’s a mix-up between 0 and 1 based counting of the months.