Raspisanie/Zurnal/UI/conver.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using OfficeOpenXml;

class Conver
{
    static void Main()
    {
        var attendanceData = new Dictionary<string, Dictionary<DateTime, bool>>
        {
            { "Студент 1", new Dictionary<DateTime, bool> { { new DateTime(2023, 10, 1), true }, { new DateTime(2023, 10, 2), false } } },
            { "Студент 2", new Dictionary<DateTime, bool> { { new DateTime(2023, 10, 1), true }, { new DateTime(2023, 10, 2), true } } }
        };

        using (ExcelPackage excel = new ExcelPackage())
        {
            foreach (var group in attendanceData)
            {
                var worksheet = excel.Workbook.Worksheets.Add(group.Key);
                worksheet.Cells[1, 1].Value = "Студент";
                int column = 2;

                foreach (var date in group.Value.Keys)
                {
                    worksheet.Cells[1, column].Value = date.ToShortDateString();
                    column++;
                }

                int row = 2;
                foreach (var student in group.Value)
                {
                    worksheet.Cells[row, 1].Value = student.Key;
                    column = 2;

                    foreach (var date in group.Value.Keys)
                    {
                        worksheet.Cells[row, column].Value = group.Value[date] ? "Присутствует" : "Отсутствует";
                        column++;
                    }
                    row++;
                }
            }

            FileInfo excelFile = new FileInfo(@"C:\Users\profi\source\Musor\Xcel\Pametka.xlsx");
            excel.SaveAs(excelFile);
        }
    }
}