C#计算相对时间

Calculate relative time in C#

提问by Jeff Atwood

Given a specific DateTimevalue, how do I display relative time, like:

给定一个特定DateTime值，我如何显示相对时间，例如：

• 2 hours ago
• 3 days ago
• a month ago

• 2小时前
• 3天前
• 一个月前

采纳答案by Vincent Robert

Jeff, your codeis nice but could be clearer with constants (as suggested in Code Complete).

杰夫，您的代码很好，但使用常量可能会更清晰（如代码完成中所建议）。

const int SECOND = 1;
const int MINUTE = 60 * SECOND;
const int HOUR = 60 * MINUTE;
const int DAY = 24 * HOUR;
const int MONTH = 30 * DAY;

var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);
double delta = Math.Abs(ts.TotalSeconds);

if (delta < 1 * MINUTE)
  return ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago";

if (delta < 2 * MINUTE)
  return "a minute ago";

if (delta < 45 * MINUTE)
  return ts.Minutes + " minutes ago";

if (delta < 90 * MINUTE)
  return "an hour ago";

if (delta < 24 * HOUR)
  return ts.Hours + " hours ago";

if (delta < 48 * HOUR)
  return "yesterday";

if (delta < 30 * DAY)
  return ts.Days + " days ago";

if (delta < 12 * MONTH)
{
  int months = Convert.ToInt32(Math.Floor((double)ts.Days / 30));
  return months <= 1 ? "one month ago" : months + " months ago";
}
else
{
  int years = Convert.ToInt32(Math.Floor((double)ts.Days / 365));
  return years <= 1 ? "one year ago" : years + " years ago";
}

回答by Jeff Atwood

Here's how I do it

这是我的方法

var ts = new TimeSpan(DateTime.UtcNow.Ticks - dt.Ticks);
double delta = Math.Abs(ts.TotalSeconds);

if (delta < 60)
{
  return ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago";
}
if (delta < 120)
{
  return "a minute ago";
}
if (delta < 2700) // 45 * 60
{
  return ts.Minutes + " minutes ago";
}
if (delta < 5400) // 90 * 60
{
  return "an hour ago";
}
if (delta < 86400) // 24 * 60 * 60
{
  return ts.Hours + " hours ago";
}
if (delta < 172800) // 48 * 60 * 60
{
  return "yesterday";
}
if (delta < 2592000) // 30 * 24 * 60 * 60
{
  return ts.Days + " days ago";
}
if (delta < 31104000) // 12 * 30 * 24 * 60 * 60
{
  int months = Convert.ToInt32(Math.Floor((double)ts.Days / 30));
  return months <= 1 ? "one month ago" : months + " months ago";
}
int years = Convert.ToInt32(Math.Floor((double)ts.Days / 365));
return years <= 1 ? "one year ago" : years + " years ago";

Suggestions? Comments? Ways to improve this algorithm?

建议？注释？改进这个算法的方法？

回答by Nick Berardi

@jeff

@杰夫

IMHO yours seems a little long. However it does seem a little more robust with support for "yesterday" and "years". But in my experience when this is used the person is most likely to view the content in the first 30 days. It is only the really hardcore people that come after that. So that is why I usually elect to keep this short and simple.

恕我直言，你的似乎有点长。然而，在支持“昨天”和“年”的情况下，它似乎更加强大。但根据我的经验，当使用它时，这个人最有可能在前 30 天内查看内容。只有真正的铁杆人才在那之后。所以这就是为什么我通常选择保持简短。

This is the method I am currently using on one of my websites. This only returns a relative day, hour, time. And then the user has to slap on "ago" in the output.

这是我目前在我的网站之一上使用的方法。这仅返回相对的日期、小时和时间。然后用户必须在输出中打上“ago”。

public static string ToLongString(this TimeSpan time)
{
    string output = String.Empty;

    if (time.Days > 0)
        output += time.Days + " days ";

    if ((time.Days == 0 || time.Days == 1) && time.Hours > 0)
        output += time.Hours + " hr ";

    if (time.Days == 0 && time.Minutes > 0)
        output += time.Minutes + " min ";

    if (output.Length == 0)
        output += time.Seconds + " sec";

    return output.Trim();
}

回答by Wedge

I thought I'd give this a shot using classes and polymorphism. I had a previous iteration which used sub-classing which ended up having way too much overhead. I've switched to a more flexible delegate / public property object model which is significantly better. My code is very slightly more accurate, I wish I could come up with a better way to generate "months ago" that didn't seem too over-engineered.

我想我会使用类和多态性来试一试。我之前有一个使用子分类的迭代，结果开销太大。我已经切换到更灵活的委托/公共属性对象模型，这明显更好。我的代码稍微准确一些，我希望我能想出一种更好的方法来生成“几个月前”，但看起来并没有过度设计。

I think I'd still stick with Jeff's if-then cascade because it's less code and it's simpler (it's definitely easier to ensure it'll work as expected).

我想我仍然会坚持使用 Jeff 的 if-then 级联，因为它的代码更少而且更简单（确保它按预期工作肯定更容易）。

For the below code PrintRelativeTime.GetRelativeTimeMessage(TimeSpan ago)returns the relative time message (e.g. "yesterday").

对于下面的代码PrintRelativeTime.GetRelativeTimeMessage(TimeSpan ago)返回相对时间消息（例如“昨天”）。

public class RelativeTimeRange : IComparable
{
    public TimeSpan UpperBound { get; set; }

    public delegate string RelativeTimeTextDelegate(TimeSpan timeDelta);

    public RelativeTimeTextDelegate MessageCreator { get; set; }

    public int CompareTo(object obj)
    {
        if (!(obj is RelativeTimeRange))
        {
            return 1;
        }
        // note that this sorts in reverse order to the way you'd expect, 
        // this saves having to reverse a list later
        return (obj as RelativeTimeRange).UpperBound.CompareTo(UpperBound);
    }
}

public class PrintRelativeTime
{
    private static List<RelativeTimeRange> timeRanges;

    static PrintRelativeTime()
    {
        timeRanges = new List<RelativeTimeRange>{
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.FromSeconds(1),
                MessageCreator = (delta) => 
                { return "one second ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.FromSeconds(60),
                MessageCreator = (delta) => 
                { return delta.Seconds + " seconds ago"; }

            }, 
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.FromMinutes(2),
                MessageCreator = (delta) => 
                { return "one minute ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.FromMinutes(60),
                MessageCreator = (delta) => 
                { return delta.Minutes + " minutes ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.FromHours(2),
                MessageCreator = (delta) => 
                { return "one hour ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.FromHours(24),
                MessageCreator = (delta) => 
                { return delta.Hours + " hours ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.FromDays(2),
                MessageCreator = (delta) => 
                { return "yesterday"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = DateTime.Now.Subtract(DateTime.Now.AddMonths(-1)),
                MessageCreator = (delta) => 
                { return delta.Days + " days ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = DateTime.Now.Subtract(DateTime.Now.AddMonths(-2)),
                MessageCreator = (delta) => 
                { return "one month ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = DateTime.Now.Subtract(DateTime.Now.AddYears(-1)),
                MessageCreator = (delta) => 
                { return (int)Math.Floor(delta.TotalDays / 30) + " months ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = DateTime.Now.Subtract(DateTime.Now.AddYears(-2)),
                MessageCreator = (delta) => 
                { return "one year ago"; }
            }, 
            new RelativeTimeRange
            {
                UpperBound = TimeSpan.MaxValue,
                MessageCreator = (delta) => 
                { return (int)Math.Floor(delta.TotalDays / 365.24D) + " years ago"; }
            }
        };

        timeRanges.Sort();
    }

    public static string GetRelativeTimeMessage(TimeSpan ago)
    {
        RelativeTimeRange postRelativeDateRange = timeRanges[0];

        foreach (var timeRange in timeRanges)
        {
            if (ago.CompareTo(timeRange.UpperBound) <= 0)
            {
                postRelativeDateRange = timeRange;
            }
        }

        return postRelativeDateRange.MessageCreator(ago);
    }
}

回答by DevelopingChris

public static string RelativeDate(DateTime theDate)
{
    Dictionary<long, string> thresholds = new Dictionary<long, string>();
    int minute = 60;
    int hour = 60 * minute;
    int day = 24 * hour;
    thresholds.Add(60, "{0} seconds ago");
    thresholds.Add(minute * 2, "a minute ago");
    thresholds.Add(45 * minute, "{0} minutes ago");
    thresholds.Add(120 * minute, "an hour ago");
    thresholds.Add(day, "{0} hours ago");
    thresholds.Add(day * 2, "yesterday");
    thresholds.Add(day * 30, "{0} days ago");
    thresholds.Add(day * 365, "{0} months ago");
    thresholds.Add(long.MaxValue, "{0} years ago");
    long since = (DateTime.Now.Ticks - theDate.Ticks) / 10000000;
    foreach (long threshold in thresholds.Keys) 
    {
        if (since < threshold) 
        {
            TimeSpan t = new TimeSpan((DateTime.Now.Ticks - theDate.Ticks));
            return string.Format(thresholds[threshold], (t.Days > 365 ? t.Days / 365 : (t.Days > 0 ? t.Days : (t.Hours > 0 ? t.Hours : (t.Minutes > 0 ? t.Minutes : (t.Seconds > 0 ? t.Seconds : 0))))).ToString());
        }
    }
    return "";
}

I prefer this version for its conciseness, and ability to add in new tick points. This could be encapsulated with a Latest()extension to Timespan instead of that long 1 liner, but for the sake of brevity in posting, this will do. This fixes the an hour ago, 1 hours ago, by providing an hour until 2 hours have elapsed

我更喜欢这个版本，因为它简洁，并且能够添加新的刻度点。这可以用Latest()Timespan的扩展来封装，而不是那条长的 1 行，但为了发布的简洁起见，这样做是可行的。 这通过提供一个小时直到 2 小时已经过去来修复一个小时前，1 小时前

回答by Will Dean

@Jeff

@杰夫

var ts = new TimeSpan(DateTime.UtcNow.Ticks - dt.Ticks);

var ts = new TimeSpan(DateTime.UtcNow.Ticks - dt.Ticks);

Doing a subtraction on DateTimereturns a TimeSpananyway.

无论如何做减法都会DateTime返回a TimeSpan。

So you can just do

所以你可以做

(DateTime.UtcNow - dt).TotalSeconds

I'm also surprised to see the constants multiplied-out by hand and then comments added with the multiplications in. Was that some misguided optimisation?

我也很惊讶地看到手动乘出常数，然后在乘法中添加注释。这是一些误导的优化吗？

回答by markpasc

When you know the viewer's time zone, it might be clearer to use calendar days at the day scale. I'm not familiar with the .NET libraries so I don't know how you'd do that in C#, unfortunately.

当您知道查看者的时区时，以天为单位使用日历日可能会更清晰。不幸的是，我不熟悉 .NET 库，所以我不知道你会如何在 C# 中做到这一点。

On consumer sites, you could also be hand-wavier under a minute. "Less than a minute ago" or "just now" could be good enough.

在消费者网站上，您也可以在一分钟内免于挥手。“不到一分钟前”或“刚刚”就足够了。

回答by markpasc

You can reduce the server-side load by performing this logic client-side. View source on some Digg pages for reference. They have the server emit an epoch time value that gets processed by Javascript. This way you don't need to manage the end user's time zone. The new server-side code would be something like:

您可以通过在客户端执行此逻辑来减少服务器端负载。查看一些 Digg 页面上的源代码以供参考。他们让服务器发出一个由 Javascript 处理的纪元时间值。这样您就不需要管理最终用户的时区。新的服务器端代码类似于：

public string GetRelativeTime(DateTime timeStamp)
{
    return string.Format("<script>printdate({0});</script>", timeStamp.ToFileTimeUtc());
}

You could even add a NOSCRIPT block there and just perform a ToString().

你甚至可以在那里添加一个 NOSCRIPT 块，然后只执行一个 ToString()。

回答by icco

In PHP, I do it this way:

在 PHP 中，我这样做：

<?php
function timesince($original) {
    // array of time period chunks
    $chunks = array(
        array(60 * 60 * 24 * 365 , 'year'),
        array(60 * 60 * 24 * 30 , 'month'),
        array(60 * 60 * 24 * 7, 'week'),
        array(60 * 60 * 24 , 'day'),
        array(60 * 60 , 'hour'),
        array(60 , 'minute'),
    );

    $today = time(); /* Current unix time  */
    $since = $today - $original;

    if($since > 604800) {
    $print = date("M jS", $original);

    if($since > 31536000) {
        $print .= ", " . date("Y", $original);
    }

    return $print;
}

// $j saves performing the count function each time around the loop
for ($i = 0, $j = count($chunks); $i < $j; $i++) {

    $seconds = $chunks[$i][0];
    $name = $chunks[$i][1];

    // finding the biggest chunk (if the chunk fits, break)
    if (($count = floor($since / $seconds)) != 0) {
        break;
    }
}

$print = ($count == 1) ? '1 '.$name : "$count {$name}s";

return $print . " ago";

} ?>

回答by Cebjyre

Surely an easy fix to get rid of the '1 hours ago' problem would be to increase the window that 'an hour ago' is valid for. Change

当然，摆脱“一小时前”问题的简单解决方法是增加“一小时前”有效的窗口。改变

if (delta < 5400) // 90 * 60
{
    return "an hour ago";
}

into

进入

if (delta < 7200) // 120 * 60
{
    return "an hour ago";
}

This means that something that occurred 110 minutes ago will read as 'an hour ago' - this may not be perfect, but I'd say it is better than the current situation of '1 hours ago'.

这意味着 110 分钟前发生的事情将读作“一小时前”——这可能并不完美，但我会说它比“1 小时前”的当前情况要好。