时间处理类

 /// <summary>
    /// 时间计算类
    /// </summary>
    public class CalculateTime
    {
        /// <summary>
        /// 计算当天是本周星期几
        /// </summary>
        /// <param name="now">当前时间</param>
        /// <returns></returns>
        public static int  CaculateWeekDay(DateTime now)
        {
            int y = now.Year;
            int m = now.Month;
            int d = now.Day;
            if (m == 1) { m = 13; y--; }
            if (m == 2) { m = 14; y--; }
            int week = (d + 2 * m + 3 * (m + 1) / 5 + y + y / 4 - y / 100 + y / 400) % 7 + 1;          
            return week;
        }
        /// <summary>
        /// 返回该周星期日的日期。
        /// </summary>
        /// <param name="now">当前时间</param>
        /// <returns></returns>
        public static DateTime GetDateOfSunday(DateTime now)
        {
            int i = CaculateWeekDay(now);
            if (i == 7)
            {
                i = 0;
            }
            return now.AddDays(-i);
        }
        /// <summary>
        /// 返回上周星期日的日期。
        /// </summary>
        /// <param name="now">当前时间</param>
        /// <returns></returns>
        public static DateTime GetDateOfLastSunday(DateTime now)
        {
            int i = CaculateWeekDay(now);
            if (i == 7)
            {
                i = 0;
            }
            return now.AddDays(-i).AddDays(-7);
        }
       /// <summary>
        /// 返回该周星期六的日期。
       /// </summary>
       /// <param name="now">当前时间</param>
       /// <returns></returns>
        public static DateTime GetDateOfSaturday(DateTime now)
        {
            int i = CaculateWeekDay(now);
            if (i == 7)
            {
                i = 0;
            }
            return now.AddDays(-i).AddDays(6);
        }
        /// <summary>
        /// 返回该周星期一的日期。
        /// </summary>
        /// <param name="now">当前时间</param>
        /// <returns></returns>
        public static DateTime GetDateOfMonday(DateTime now)
        {
            int i = CaculateWeekDay(now);
            if (i == 7)
            {
                i = 0;
            }
            return now.AddDays(-i).AddDays(1);
        }
        /// <summary>
        /// 计算当天所在的周是当年的第几周
        /// </summary>
        /// <param name="now">当前时间</param>
        /// <returns></returns>
        public static int GetWeekNumOfYear(DateTime now)
        {
            int days = now.DayOfYear + (7 - (int)now.DayOfWeek);
            return days / 7 + (days % 7 == 0 ? 0 : 1);
        }

 

    }