我的Cookie何时真正过期？ [英] When will my cookie actually expire?

问题描述

我在加利福尼亚的服务器上运行着一个ASP.NET应用程序。服务器的当前时间是：

I have an ASP.NET application running on a server in California. The server's current time is:

• 2015/7/20 14:00 UTC-08：00

Bob已连接到我的服务器。鲍勃在德克萨斯州。他当前的时间是：

Bob is connected to my server. Bob is in Texas. His current time is:

• 2015/7/20 16:00 UTC-06：00

我的应用程序创建一个cookie并设置其过期日期。

My application creates a cookie and set its expiration date.

var name = "MyName";
var value = "MyValue"
var hoursToLive = 24;

var myCookie = new HttpCookie(name )
{
    Value = value,
    Expires = DateTime.Now.AddHours(hoursToLive)
};

该Cookie会在24小时后过期，还是会在22小时后过期（由于两者之间的时间差）鲍勃和服务器？我知道 DateTime.Now使用服务器的本地时间，但是我不清楚浏览器如何确定Cookie过期（具体来说，使用哪个时区来确定到期时间。）

Will the cookie expire in 24 hours, or will it expire in 22 hours due to the time difference between Bob and the server? I know that DateTime.Now uses the server's local time, but I am unclear as to how browsers decide that a cookie is expired (specifically, what time zone is used to determine expiration).

推荐答案

Cookie的时区信息中包含过期标头（主要是格林尼治标准时间），这使得客户端很容易处理服务器实际时区的偏移量。

Cookies do include a timezone information with the expires header (mostly GMT), which makes it quite simple for the client to cope with the offset to the server's actual timezone.

示例：如果 2015-07-20 14:00:00 UTC-8， expires =星期一，2015年7月20日22:00:00 GMT 是服务器的时间。当客户端或服务器决定Cookie是否过期时，它将与相关的GMT时间进行比较。

Example: expires=Mon,20-Jul-2015 22:00:00 GMT if 2015-07-20 14:00:00 UTC-8 is the server's time. When the client or server decides whether the cookie is expired or not, it will compare it to the associated GMT time.

我更深入地研究了 System.Web.HttpCookie ，以及在 GetSetCookieHeader（）中找到了相关代码：

I dug deeper into the code of System.Web.HttpCookie, and found the relevant code in GetSetCookieHeader():

        if (_expirationSet && _expires != DateTime.MinValue) {
            s.Append("; expires=");
            s.Append(HttpUtility.FormatHttpCookieDateTime(_expires));
        }

其中 HttpUtility.FormatHttpCookieDateTime（） 返回UTC时间戳（不包含偏移量，

Where HttpUtility.FormatHttpCookieDateTime() returns a UTC timestamp (with no offset, which doesn't matter because the offset would be zero).

在大多数情况下，格林威治标准时间（GMT）和世界协调时间（UTC）可以认为是相同的。您可以在此处了解更多信息。

Greenwich Mean Time (GMT) and Coordinated Universal Time (UTC) can, for most purposes, be considered the same. You can read more about this here.

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