DateTime Extension Methods for first and last days of the month

I have seen several articles on how to derive the first and last day of the month from a given date. This method uses .Net 4.0 extension methods, which is a more elegant solution.

using System;

namespace MRMPortal.Service.Extensions
{
    public static class DateTimeExtensionMethods
    {
        public static DateTime FirstDayOfMonth(this DateTime value)
        {
            return new DateTime(value.Year, value.Month, 1);
        }

        public static DateTime LastDayOfMonth(this DateTime value)
        {
            return new DateTime(value.Year, value.Month, 1).AddMonths(1).AddDays(-1);
        }
    }
}