请教论坛评论上面看到的“于1月前说 ”“于4分钟前说”代码怎样写

public class CalculationTimes    {        public static string CalculationTime(DateTime Starttime)        {            string timeString = "";            DateTime EndTime = DateTime.Now;            if (EndTime < Starttime)                return "开始时间不能大于当前时间";            TimeSpan span = EndTime - Starttime;            if (span.Days > 365)                timeString = (span.Days / 365).ToString() + "年前";            else if (span.Days > 30)                timeString = (span.Days / 30).ToString() + "个月前";            else if (span.Days > 0)                timeString = span.Days.ToString() + "天前";            else if (span.Hours > 0)                timeString = span.Hours.ToString() + "小时前";            else if (span.Minutes > 0)                timeString = span.Minutes.ToString() + "分钟前";            else if (span.Seconds > 0)                timeString = span.Seconds.ToString() + "秒前";            else                timeString = "刚刚";            return timeString;        }    }