C#中的DateTime函数

DateTime dt = new DateTime(2011, 3, 4);
DateTime dt3 = new DateTime(2011, 3, 4, 17, 08, 09);
DateTime dt1 = DateTime.Now;
DateTime dt2 = DateTime.Today;
DateTime dt5 = new DateTime(20000, DateTimeKind.Local);

DateTime dt4 = new DateTime(1983, 5, 17, new System.Globalization.ChineseLunisolarCalendar()); //农历日期
Console.WriteLine(dt4); //1983/6/27 0:00:00

DateTime dt = DateTime.Now;
s1=dt.ToString();//2019-06-25 10:38:31
s2=dt.ToString("d");//2019-06-25

s3=dt.toToLocalTime().ToString();//2019-06-25 10:38:31
s4=dt.ToUniversalTime().ToString();//2019-06-25 2:38:31

s1 = dt.ToLongDateString(); // 2019年6月25日
s2 = dt.ToShortDateString();// 2019-06-25
s3 = dt.ToLongTimeString(); // 10:41:14
s4 = dt.ToShortTimeString();// 10:41

s1 = dt.Date.ToString();//日期。2019-06-25 0:00:00
s2 = dt.Year.ToString();//年。2019
s3 = dt.Month.ToString();//月。6
s4 = dt.Day.ToString();//日。 25
s5 = dt.DayOfWeek.ToString();//星期。Tuesday
s6 = Convert.ToInt32(dt.DayOfWeek).ToString(); //2
s7 = dt.DayOfYear.ToString();// 该年中的第几天。176
s8 = (dt.DayOfYear / 7 + 1).ToString();//该年中的第几周。26

s1 = dt.TimeOfDay.ToString();//时间。10:50:23.4881958
s2 = dt.Hour.ToString();//时，10
s3 = dt.Minute.ToString();//分、50
s4 = dt.Second.ToString();//秒 23
s5 = dt.Millisecond.ToString();//毫秒。 488

s1 = dt.Ticks.ToString();//一个tick代表100ns，一毫秒=10000tick,一秒等于107个ticks.636970570197681958

s1 = dt.AddYears(1).ToString();// 2020-06-25 11:01:09
s2 = dt.AddMonths(-1).ToString();// 2019-05-25 11:01:24
s3 = dt.AddDays(1).ToString();// 2019-06-26 11:01:24
s4 = dt.AddHours(-1).ToString();// 2019-06-25 10:01:24
s5 = dt.AddMinutes(1).ToString();//2019-06-25 11:02:24
s6 = dt.AddTicks(1000).ToString();//2019-06-25 11:01:24

DateTime dt = DateTime.Now;

s1 = dt + TimeSpan.FromDays(2.1).ToString();//2019-06-25 11:05:392.02:24:00
s2 = dt.Add(TimeSpan.FromDays(2.1)).ToString();//2019-06-27 13:29:39
s3 = (dt - new TimeSpan(1, 2, 0, 0, 0)).ToString();// 2019-06-24 9:05:39
s4 = dt.Subtract(TimeSpan.FromDays(2)).ToString();//2019-06-23 11:05:39

s1 = (dt - dt.AddDays(-3)).Days.ToString();//3
s2 = (dt.Subtract(dt.AddDays(-3))).Days.ToString();//3

s1 = dt.CompareTo(dt.AddYears(1)).ToString();//-1
s2 = (dt == dt.AddYears(1)).ToString();//False
s3 = (dt < dt.AddYears(1)).ToString();// True

s1 = DateTime.DaysInMonth(2019, 6).ToString();//某月共有几天,30
s2 = DateTime.IsLeapYear(2019).ToString();    //是否为闰年,False
s3 = DateTime.Compare(dt, new DateTime(2019, 6, 25))) //比较. 1

s4 = DateTime.Parse("2019,5,16").ToString();//2019-05-16 0:00:00
s5 = DateTime.ParseExact("1899-12-30", "yyyy-MM-dd", CultureInfo.CurrentCulture.DateTimeFormat).ToString();//1899-12-30 0:00:00
s6 = Convert.ToDateTime("2019,5,16").ToString();//2019-05-16 0:00:00

GregorianCalendar gc = new GregorianCalendar();
int weekOfYear = gc.GetWeekOfYear(DateTime.Now, CalendarWeekRule.FirstDay, DayOfWeek.Monday);
s1 = weekOfYear.ToString();// 26

// 将时间变成数字,同JS的d.GetTime()相同的值，到毫秒三种方式
var a = (DateTime.Now.ToUniversalTime().Ticks - 621355968000000000) / 10000;
var b = (DateTime.Now.ToUniversalTime().Ticks - new DateTime(1970, 1, 1).Ticks) / 10000;
var c = (Int64)(DateTime.Now.ToUniversalTime() - new DateTime(1970, 1, 1)).TotalMilliseconds;
//将数字变成时间(本地时间)，同JS中的 var d= new Date(100000000000)。
var d = DateTime.Parse("1970-01-01 00:00:00").AddMilliseconds(c);
Console.WriteLine(a);
Console.WriteLine(b);
Console.WriteLine(c);
Console.WriteLine(d.ToLocalTime());

//输出：
//1620634282422
//1620634282422
//1620634282422
//2021/5/10 星期一 16:11:22