Formula adds one day to Max dates

I use two formulas that return Min and Max date of children to create a “total span”.
The Max date gets an entire day added to it.

I have not done further testing on when this happens.

ETA: Date with Start and End.

Start Date: Formula with Features.Min(ETA.Start)
End Date: Formula with Features.Max(ETA.End)

Result visualized using timeline:

Related to this I suspect.
It would be nice to know how dates (without times) are managed under-the-hood, because I’ve experienced a few similar issues.