using System;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        var ptBR = new CultureInfo("pt-BR");

        Console.WriteLine($"Hoje é: {ptBR.DateTimeFormat.GetDayName(DateTime.Now.DayOfWeek)}");

        var data = DateTime.Now.ToString("'Hoje é: ' dd 'de' MMMM 'de' yyyy", new CultureInfo("pt-BR"));

        Console.WriteLine(data);

        var data2 = DateTime.Now.ToString("dd/MM/yyyy HH:mm:ss");

        Console.WriteLine(data2);       

    }

}