Yep, that's right. But I guess that's only a matter of implementation thow.

I really would love to agree on the status of this issue in first hand, before moving to a (more robust) implementation.

If you think, that the current implementation is fine, I'm going to implement my own daysAsSql method for my project separately. 

To put it in a nutshell:
A method returning always 00:00:00 to 23:59:59 is fine for every case, where no timezone is involved.
A method returning an unexpected date because of a timezone setting generates frustration. 

So, for me, there are 2 options:

1. remove the timezone param for the current implementation
2. change the current implementation to the proposed one and make the implementation more robust to fix the mentioned problems above.