.NET Get the first and last day of the given date

How Get the first and last day of the given date

// get First day date
    public static DateTime GetFirstDayOfMonth(DateTime givenDate)
    {
         return new DateTime(givenDate.Year, givenDate.Month, 1);
    }

//get last day date

    public static DateTime GetTheLastDayOfMonth(DateTime givenDate)
    {
         return GetFirstDayOfMonth(givenDate).AddMonths(1).Subtract(new TimeSpan(1, 0, 0, 0, 0));
    }