Mark ranges between two years in the Excel 2013 workbook.

ExcelLifeBookRanges.cs

private void MarkKinderkarden(int fromYear, int toYear)
{
    MarkRange(fromYear, toYear, Color.SteelBlue);
}
        
private void MarkRange(int fromYear, int toYear, Color color)
{
    var dayStart = fromYear*365;
    var dayEnd = toYear*365;

    // Calculate the row and column of the starting cell for the range.
    var startRow = Math.Ceiling(dayStart/170.0f);
    var startColumn = dayStart%170;

    for (var day = dayStart; day < dayEnd; day++)
    {
        var cell = Cells[startRow, startColumn++] as Range;
        if (cell != null) cell.Interior.Color = color;

        if (startColumn > 170)
        {
            startColumn = 1;
            startRow++;

            if (startRow > 170)
            {
                startRow = 1;
            }
        }
    }
}