docs: protected int getInternalDayFromLocation(float x, float y) {
          int dayStart = mEdgePadding;
          if (x < dayStart || x > mWidth - mEdgePadding) {
              return -1;
          }
          // Selection is (x - start) / (pixels/day) == (x -s) * day / pixels
          int row = (int) (y - getMonthHeaderSize()) / mRowHeight;
          int column = (int) ((x - dayStart) * mNumDays / (mWidth - dayStart - mEdgePadding));
  
          int day = column - findDayOffset() + 1;
          day += row * mNumDays;
          return day;
      }