/// <summary>

    /// DateTimeHelper

    /// </summary>

    public static class DateTimeHelper

    {

        /// <summary>

        /// Unix时间起始时间

        /// </summary>

        public static readonly DateTime StarTime = new DateTime(, , );

        /// <summary>

        /// 常用日期格式

        /// </summary>

        public static readonly string CommonDateFormat = "yyyy-MM-dd HH:mm:ss.fff";

        /// <summary>

        /// 周未定义

        /// </summary>

        public static readonly DayOfWeek[] Weekend = { DayOfWeek.Saturday, DayOfWeek.Sunday };

        /// <summary>

        /// 获取从Unix起始时间到给定时间的毫秒数

        /// </summary>

        /// <param name="datetime"></param>

        /// <returns></returns>

        public static long GetMillisecondsSince1970(this DateTime datetime)

        {

            var ts = datetime.Subtract(StarTime);

            return (long)ts.TotalMilliseconds;

        }

        /// <summary>

        /// 获取从Unix起始时间到给定时间的秒数

        /// </summary>

        /// <param name="datetime"></param>

        /// <returns></returns>

        public static long GetSecondsSince1970(this DateTime datetime)

        {

            var ts = datetime.Subtract(StarTime);

            return (long)ts.TotalSeconds;

        }

        /// <summary>

        /// 明天

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static DateTime Tomorrow(this DateTime date)

        {

            return date.AddDays();

        }

        /// <summary>

        /// 昨天

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static DateTime Yesterday(this DateTime date)

        {

            return date.AddDays(-);

        }

        /// <summary>

        /// 常用日期格式化字符串

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static string ToCommonFormat(this DateTime date)

        {

            return date.ToString(CommonDateFormat);

        }

        /// <summary>

        /// 是否是周未

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static bool IsWeekend(this DateTime date)

        {

            return Weekend.Any(p => p == date.DayOfWeek);

        }

        /// <summary>

        /// 是否是工作日

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static bool IsWeekDay(this DateTime date)

        {

            return !date.IsWeekend();

        }

        /// <summary>

        /// 给定月份的第1天

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static DateTime GetFirstDayOfMonth(this DateTime date)

        {

            return new DateTime(date.Year, date.Month, );

        }

        /// <summary>

        /// 给定月份的最后1天

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static DateTime GetLastDayOfMonth(this DateTime date)

        {

            return date.GetFirstDayOfMonth().AddMonths().AddDays(-);

        }

        /// <summary>

        /// 给定日期所在月份第1个星期几所对应的日期

        /// </summary>

        /// <param name="date">给定日期</param>

        /// <param name="dayOfWeek">星期几</param>

        /// <returns>所对应的日期</returns>

        public static DateTime GetFirstWeekDayOfMonth(this DateTime date, DayOfWeek dayOfWeek)

        {

            var dt = date.GetFirstDayOfMonth();

            while (dt.DayOfWeek != dayOfWeek)

                dt = dt.AddDays();

            return dt;

        }

        /// <summary>

        /// 给定日期所在月份最后1个星期几所对应的日期

        /// </summary>

        /// <param name="date">给定日期</param>

        /// <param name="dayOfWeek">星期几</param>

        /// <returns>所对应的日期</returns>

        public static DateTime GetLastWeekDayOfMonth(this DateTime date, DayOfWeek dayOfWeek)

        {

            var dt = date.GetLastDayOfMonth();

            while (dt.DayOfWeek != dayOfWeek)

                dt = dt.AddDays(-);

            return dt;

        }

        /// <summary>

        /// 早于给定日期

        /// </summary>

        /// <param name="date"></param>

        /// <param name="other"></param>

        /// <returns></returns>

        public static bool IsBefore(this DateTime date, DateTime other)

        {

            return date.CompareTo(other) < ;

        }

        /// <summary>

        /// 晚于给定日期

        /// </summary>

        /// <param name="date"></param>

        /// <param name="other"></param>

        /// <returns></returns>

        public static bool IsAfter(this DateTime date, DateTime other)

        {

            return date.CompareTo(other) > ;

        }

        /// <summary>

        /// 给定日期最后一刻,精确到23:59:59.999

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static DateTime EndTimeOfDay(this DateTime date)

        {

            return new DateTime(date.Year, date.Month, date.Day, , , , );

        }

        /// <summary>

        ///  给定日期开始一刻,精确到0:0:0.0

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static DateTime StartTimeOfDay(this DateTime date)

        {

            return date.Date;

        }

        /// <summary>

        ///  给定日期的中午,精确到12:0:0.0

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static DateTime NoonOfDay(this DateTime date)

        {

            return new DateTime(date.Year, date.Month, date.Day, , , );

        }

        /// <summary>

        /// 当前日期与给定日期是否是同一天

        /// </summary>

        /// <param name="date">当前日期</param>

        /// <param name="dateToCompare">给定日期</param>

        /// <returns></returns>

        public static bool IsDateEqual(this DateTime date, DateTime dateToCompare)

        {

            return (date.Date == dateToCompare.Date);

        }

        /// <summary>

        /// 判断是否为今天

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static bool IsToday(this DateTime date)

        {

            return (date.Date == DateTime.Now.Date);

        }

        /// <summary>

        /// 给定日期所在月份共有多少天

        /// </summary>

        /// <param name="date"></param>

        /// <returns></returns>

        public static int GetCountDaysOfMonth(this DateTime date)

        {

            return date.GetLastDayOfMonth().Day;

        }

    }