using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("//0. 기준날짜");

        DateTime dateToday = DateTime.Today;

        Console.WriteLine("//결과 : " + dateToday.ToString());

        Console.WriteLine("DateTime dateToday = DateTime.Today;");

​

        Console.WriteLine(" ");

​

        Console.WriteLine("//0-2. 오늘 요일");

        Console.WriteLine("//결과 : " + dateToday.DayOfWeek.ToString());

        Console.WriteLine("DateTime dateToday = DateTime.Today;");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//1. 이번달 1일");

        DateTime dtFirstDay = dateToday.AddDays(1 - dateToday.Day);

        Console.WriteLine("//결과 : " + dtFirstDay.ToString());

        Console.WriteLine("DateTime dtFirstDay = dateToday.AddDays(1 - dateToday.Day);");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//2-1. 요번달 마지막날짜");

        DateTime dtMonthLastDay = dateToday.AddMonths(1).AddDays(-dateToday.Day);

        Console.WriteLine("//결과 : " + dtMonthLastDay.ToString());

        Console.WriteLine("DateTime dtMonthLastDay = dateToday.AddMonths(1).AddDays(dateToday.Day);");

        Console.WriteLine(" ");

        //https://learn.microsoft.com/ko-kr/dotnet/api/system.datetime.daysinmonth?view=net-7.0

        Console.WriteLine("//2-2. 요번달 마지막날짜");

        int nMonthLastDay2_Day = DateTime.DaysInMonth(dateToday.Year, dateToday.Month);

        DateTime dtMonthLastDay2 = new DateTime(dateToday.Year, dateToday.Month, nMonthLastDay2_Day);

        Console.WriteLine("//결과 : " + dtMonthLastDay2.ToString());

        Console.WriteLine("int nMonthLastDay2_Day = DateTime.DaysInMonth(dateToday.Year, dateToday.Month);");

        Console.WriteLine("DateTime dtMonthLastDay2 = new DateTime(dateToday.Year, dateToday.Month, nMonthLastDay2_Day);");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//3. 요번주의 남은 날짜(오늘포함, 토요일까지만)");

        int intWeekLeftDayCount = 7 - (int)(dtFirstDay.DayOfWeek);

        Console.WriteLine("//결과 : " + intWeekLeftDayCount.ToString());

        Console.WriteLine("int intWeekLeftDayCount = 7 - (int)(dtFirstDay.DayOfWeek);");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//4. 요번달의 첫 일요일(1일 기준이기 때문에 1일이 일요일이 아니면 전달 마지막 일요일이 표시됨.)");

        DateTime dtMonthFirstSunday = dtFirstDay.AddDays(0 - (int)(dtFirstDay.DayOfWeek));

        Console.WriteLine("//결과 : " + dtMonthFirstSunday.ToString());

        Console.WriteLine("DateTime dtMonthFirstSunday = dtFirstDay.AddDays(0 - (int)(dtFirstDay.DayOfWeek));");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//5. 마지막 주의 일요일");

        DateTime dtLastSunday = dtMonthLastDay.AddDays(0 - (int)(dtMonthLastDay.DayOfWeek));

        Console.WriteLine("//결과 : " + dtLastSunday.ToString());

        Console.WriteLine("DateTime dtLastSunday = dtMonthLastDay.AddDays(0 - (int)(dtMonthLastDay.DayOfWeek));");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//6. 마지막 주의 일수");

        int intLastWeekDayCount = dtMonthLastDay.DayOfYear - dtLastSunday.DayOfYear + 1;

        Console.WriteLine("//결과 : " + intLastWeekDayCount.ToString());

        Console.WriteLine("int intLastWeekDayCount = dtMonthLastDay.DayOfYear - dtLastSunday.DayOfYear + 1;");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//7. 이번 달의 주수를 가져오는 방법");

        int intMonthWeekCount = ((dtMonthLastDay.DayOfYear - dtMonthFirstSunday.AddDays(7).DayOfYear) / 7) + 2;

        Console.WriteLine("//결과 : " + intMonthWeekCount.ToString());

        Console.WriteLine("int intMonthWeekCount = ((dtMonthLastDay.DayOfYear - dtMonthFirstSunday.AddDays(7).DayOfYear) / 7) + 2;");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//8. 영어날짜");

        string strNowEng = String.Format(new System.Globalization.CultureInfo("en-US"), "{0:dddddddddd} {0:MMMMMMMM} {0:d} {0:hh}:{0:mm}:{0:ss} {0:yyyy}", dateToday.ToUniversalTime());

        Console.WriteLine("//결과 : " + strNowEng.ToString());

        Console.WriteLine("string strNowEng = String.Format(new System.Globalization.CultureInfo(\"en-US\"), \"{0:dddddddddd} {0:MMMMMMMM} {0:d} {0:hh}:{0:mm}:{0:ss} {0:yyyy}\", dateToday.ToUniversalTime());");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

        Console.WriteLine("//9-1. 요번주의 원하는 요일의 날짜 구하기(여기서는 금요일)");

        DateTime fridayDate = dateToday.AddDays(Convert.ToInt32(DayOfWeek.Friday) - Convert.ToInt32(dateToday.DayOfWeek));

        Console.WriteLine("//결과 : " + fridayDate.ToString());

        Console.WriteLine("DateTime fridayDate = dateToday.AddDays(Convert.ToInt32(DayOfWeek.Friday) - Convert.ToInt32(dateToday.DayOfWeek));");

​

        Console.WriteLine(" ");

​

        Console.WriteLine("//9-2. 요번주의 일요일 날짜");

        DateTime dateSunday = dateToday.AddDays(Convert.ToInt32(DayOfWeek.Sunday) - Convert.ToInt32(dateToday.DayOfWeek));

        Console.WriteLine("//결과 : " + dateSunday.ToString());

        Console.WriteLine("DateTime dateSunday = dateToday.AddDays(Convert.ToInt32(DayOfWeek.Sunday) - Convert.ToInt32(dateToday.DayOfWeek));");

​

        Console.WriteLine(" ");

        Console.WriteLine(" ");

​

    }

}