using System;

using static System.Console;

public class Program {

    public static void Main() {

        var data = new DateTime(2015, 8, 15);

        WriteLine(FirstDayPreviousMonth(data));

        WriteLine(LastDayPreviousMonth(data));

        data = new DateTime(2015, 3, 15);

        WriteLine(FirstDayPreviousMonth(data));

        WriteLine(LastDayPreviousMonth(data));

        data = new DateTime(2016, 3, 15);

        WriteLine(FirstDayPreviousMonth(data));

        WriteLine(LastDayPreviousMonth(data));

    }

    public static DateTime FirstDayPreviousMonth(DateTime date) {

        var mesAnterior = date.AddMonths(-1);

        return new DateTime(mesAnterior.Year, mesAnterior.Month, 1); 

    }

    public static DateTime LastDayPreviousMonth(DateTime date) {

        var mesAnterior = date.AddMonths(-1);

        return new DateTime(mesAnterior.Year, mesAnterior.Month, DateTime.DaysInMonth(mesAnterior.Year, mesAnterior.Month));

    }

}