code: public int getDayFromLocation(float x, float y) {
          final int day = getInternalDayFromLocation(x, y);
          if (day < 1 || day > mNumCells) {
              return -1;
          }
          return day;
      }
docs: Calculates the day that the given x position is in, accounting for week
  number. Returns the day or -1 if the position wasn't in a day.
  
  @param x The x position of the touch event
  @return The day number, or -1 if the position wasn't in a day