DateTime offen use (常用功能)

 

请移步到: Date and Time 日期时间 – 开发中的基础知识

 

更新 : 2017-10-11 

https://docs.microsoft.com/en-us/sql/t-sql/functions/date-and-time-data-types-and-functions-transact-sql

 

 

public partial class HTML4_date_time_js_Default : System.Web.UI.Page

{

    public static int getww(DateTime time)
    {
        // Seriously cheat.  If its Monday, Tuesday or Wednesday, then it'll 
        // be the same week# as whatever Thursday, Friday or Saturday are,
        // and we always get those right
        DayOfWeek day = CultureInfo.InvariantCulture.Calendar.GetDayOfWeek(time);
        if (day >= DayOfWeek.Monday && day <= DayOfWeek.Wednesday)
        {
            time = time.AddDays(3);
        }

        // Return the week of our adjusted day
        return CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(time, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
    }

    public static int getquarter(DateTime date)
    {
        if (date.Month >= 1 && date.Month <= 3)
            return 1;
        else if (date.Month >= 4 && date.Month <= 6)
            return 2;
        else if (date.Month >= 7 && date.Month <= 9)
            return 3;
        else
            return 4;
    }


    protected void Page_Load(object sender, EventArgs e)
    {
       //当前时间 
        string datetime = DateTime.Now.ToString("MM_dd_yyyy") + "_" + DateTime.Now.Hour.ToString() + "_" + DateTime.Now.Minute.ToString() + "_" + DateTime.Now.Millisecond.ToString();
        
        //set a date 
        DateTime dt_date = new DateTime(2013, 10, 07, 00, 05, 00, 00);

        //add day / month / year 
        DateTime dt_last_day = dt_date.AddDays(-1);

        // to string 
        string last_day = dt_last_day.ToString("yyyy-MM-dd");

        //get 星期几 result : monday
        string day = (Convert.ToDateTime(dt_last_day).DayOfWeek.ToString());

        //get year
        string year = dt_last_day.Year.ToString();

        //get month 
        string month = dt_last_day.Month.ToString();

        //get jam 
        string jam = DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss tt", new CultureInfo("en-US")); // output : 2012-06-24 02:40:23 AM
        jam = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss fff", new CultureInfo("en-US")); // output : 2012-06-24 02:40:23:256 国际时间

        // 获取当月最后一天  result : 29
        int last_day_of_month = System.DateTime.DaysInMonth(2000, 02);


        //算第几个 work week 
        string ww = getww(dt_last_day).ToString();

        //get 季度
        string quarter = getquarter(dt_last_day).ToString();



        //时间差 
        DateTime today = DateTime.Now;  //today
        DateTime last_night = DateTime.Now.AddDays(-1); //last night
        
        //compare 大小
        int result = DateTime.Compare(today, last_night); //if result < 0  (A early than B) para 1 比较早 ， = 0 同一天 ,>0 就是迟咯


        TimeSpan chabie = today.Subtract(last_night); //对比时间差
        double double_chabie = chabie.TotalMilliseconds; //convert to milisecond 
        double_chabie = Math.Round(double_chabie, 0); // round up to 没有小数点
        double_chabie = double_chabie / 1000 / 60 / 60 / 24; // formula to unit 天 

        // String to DateTime
        String MyString = "1999-09-01 21:34 PM";
        //MyString = "1999-09-01 21:34 p.m.";  //Depends on your regional settings
        DateTime MyDateTime;
        MyDateTime = new DateTime();
        MyDateTime = DateTime.ParseExact(MyString, "yyyy-MM-dd HH:mm tt", new CultureInfo("en-US"));
        
        //DateTime to String
        MyDateTime = new DateTime(1999, 09, 01, 21, 34, 00);
        MyString = MyDateTime.ToString("yyyy-MM-dd HH:mm tt", new CultureInfo("en-US"));



        // timezone 处理
        DateTime dt = TimeZoneInfo.ConvertTimeToUtc(DateTime.Now, TimeZoneInfo.Local); //当前本地时间
        string a = dt.ToString("yyyy-MM-dd hh:mm:ss tt", new CultureInfo("en-US"));
        dt = TimeZoneInfo.ConvertTimeFromUtc(dt, TimeZoneInfo.FindSystemTimeZoneById("Singapore Standard Time")); //convert to 指定的区域 
        a = dt.ToString("yyyy-MM-dd hh:mm:ss tt", new CultureInfo("en-US"));
        a = "";
        ReadOnlyCollection<TimeZoneInfo> lst = TimeZoneInfo.GetSystemTimeZones(); //获取所有可以convert to 的list 比如 Singapore Standard Time
        foreach (TimeZoneInfo tzi in lst)
        {
            a = a == "" ? tzi.Id : a + "\r\n" + tzi.Id;
        }


        //在某个时间内
        //方便下次调用 
        DateTime now = DateTime.Now;
        string day123 = now.DayOfWeek.ToString();
        if (day123 == "Monday")
        {
            DateTime start = DateTime.ParseExact("00:00:00", "HH:mm:ss", new CultureInfo("en-US"));  
            DateTime end = DateTime.ParseExact("00:15:00", "HH:mm:ss", new CultureInfo("en-US"));
            if (DateTime.Compare(now, start) >= 0 && DateTime.Compare(now, end) <= 0)
            {
                //do something
            }
        }


        //指定一个时间内连续触发，但是成功后就不做了(cache up 成功) 方便下次调用
        DateTime start1 = new DateTime(now.Year, now.Month, now.Day, now.Hour, 00, 00, 000); 
        DateTime end1 = new DateTime(now.Year, now.Month, now.Day, now.Hour, 05, 00, 000);
        if (DateTime.Compare(now, start1) >= 0 && DateTime.Compare(now, end1) < 0)
        {
            if (Cache["key"] == null)
            {
                double gap = end1.Subtract(now).TotalMilliseconds;
                Cache.Add("key", "x", null, DateTime.Now.AddMilliseconds(gap), Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, null);
            }
        }
    }
}

 

 

 

想判断一个时间有没有在几点到几点之间 

TimeSpan startTime = new TimeSpan(7,0,0);
TimeSpan endTime = new TimeSpan(2, 59, 0);

if (DateTime.Now.TimeOfDay >= startTime &&
    DateTime.Now.TimeOfDay <= endTime)
{
    //in range
}
else
{
    //not in range. 

}

 

更新 : 2015-11-19 

DateTime xx = new DateTime(2015, 1, 30).AddMonths(1);  

c# 的 AddMonths 和 js 的都是用 setMonth 的概念，区别是js 会因为day超出当月份时“自动”往后加多几天，导致月份跟可能随着改变, C#则完全不会"自动".