Calculate birthdays and visualize them in the 170 x 170 area of the Excel 2013 workbook.

ExcelLifeBookBirthdays.cs

private void CalculateBirthdays(int rows, int columns)
{
    var days = 1;
    var years = 1;

    for (var row = 1; row <= rows; row++)
    {
        for (var column = 1; column <= columns; column++)
        {
            var cell = Cells[row, column] as Range;

            if (cell != null && days % 365 == 0)
            {
                cell.Interior.Color = Color.Green;
                Cells[row, column] = years;

                years++;
            }

            days++;
        }
    }
}