in my reports, I am often using relative intervals such as "Today", "Yesterday", "This week", "Previous week", "Last 7 days", etc.

I have a "Relative date" dropdown menu with indexes, than "post-processing formula" in DATE picker, that overwrite DATE if specific "Relative date" is chosen.

While most of them are working as they should, I have problem with interval "Yesterday" at the beginning of the month.

The interval is defined as formula:
However, it returned 30.8. instead of 31.8. when I ran it 1.9. (this friday).

I am running pentaho 7.1 CE and report_designer 7.1 too.

Does anybody encountered this problem? Is there any chance how to fix it? Or perhaps, am I doing anything wrong?