DateTime Conversion in C#

Try this function

private static DateTime? GetTime(string s)
{
    var regex = new Regex(
                    @"^[\-drswx]{10}\s+\d+\s+ftp\s+ftp\s+\d+\s+" +
                    @"(?<Month>[a-zA-Z]{3})\s+(?<Day>\d{1,2})\s+" +
                    @"(?<Hours>\d{2})\:(?<Mins>\d{2})\s+.*$");

    var m = regex.Match(s);

    DateTime? result = null;

    if (m.Success)
    {
        var year = DateTime.Now.Year.ToString();
        var month = m.Groups["Month"].ToString();
        var day = m.Groups["Day"].ToString();
        var hours = m.Groups["Hours"].ToString();
        var mins = m.Groups["Mins"].ToString();

        var timepart = string.Format(@"{0}/{1}/{2} {3}:{4}", year, month, day, hours, mins);

        result = DateTime.ParseExact(timepart, "yyyy/MMM/dd HH:mm"
                , new CultureInfo("en-US"));

        if (result.Value.Month > DateTime.Now.Month)
        {
            result.Value.AddYears(-1);
        }
    }
    else
    {
        regex = new Regex(
                    @"^[\-drswx]{10}\s+\d+\s+ftp\s+ftp\s+\d+\s+" +
                    @"(?<Month>[a-zA-Z]{3})\s+(?<Day>\d{1,2})\s+" +
                    @"(?<Year>\d{4})\s+.*$");
            
        m = regex.Match(s);

        if (!m.Success)
        {
            return null;
        }

        var year = m.Groups["Year"].ToString();
        var month = m.Groups["Month"].ToString();
        var day = m.Groups["Day"].ToString();

        var timepart = string.Format(@"{0}/{1}/{2}", year, month, day);

        result = DateTime.ParseExact(timepart, "yyyy/MMM/dd", new CultureInfo("en-US"));
    }
    return result;
}