为什么DateTime.AddHours似乎不起作用？

问题描述

我有相同的结果1338161400当我做

I have same result 1338161400 when I do

    DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0);
    DateTime date = DateTime.Parse(@"28/05/12 01:30");
    TimeSpan diff = date.ToUniversalTime() - origin;
    Console.WriteLine( (Math.Floor(diff.TotalSeconds)).ToString());

以及当我使用date.AddHours（-4）：

as well as when I use date.AddHours(-4) :

    DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0);
    DateTime date = DateTime.Parse(@"28/05/12 01:30");
    date.AddHours(-4);
    TimeSpan diff = date.ToUniversalTime() - origin;
    Console.WriteLine( (Math.Floor(diff.TotalSeconds)).ToString());

我尝试得到1338168600像

I try to get 1338168600 like http://www.mbari.org/staff/rich/utccalc.htm

更新：

感谢我更改为

    DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0);
    DateTime date = DateTime.Parse(@"28/05/2012 01:30");
    date = date.AddHours(-4);
    date = date.ToUniversalTime();
    TimeSpan diff = date - origin;
    Console.WriteLine((Math.Floor(diff.TotalSeconds)).ToString());

但是我还有1338147000还没有1338168600

But I got 1338147000 still not 1338168600

推荐答案

日期是不可变的对象，即创建后无法修改。 DateTime.AddHours返回一个新的DateTime实例，该实例向后移动4个小时，但date将不被修改。

Dates are immutable objects, i.e. they cannot be modified after creation. DateTime.AddHours returns a new DateTime instance which is shifted backwards by 4 hours but "date" will not be modified.

使用：

DateTime newDate = date.AddHours(-4);

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