Calculate relative time in C#

Question

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

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

Answer 1

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

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";
}

Answer 2

If you want to have an output like "2 days, 4 hours and 12 minutes ago", you need a timespan:

TimeSpan timeDiff = DateTime.Now-CreatedDate;

Then you can access the values you like:

timeDiff.Days
timeDiff.Hours

etc...

Answer 3

/** 
 * {@code date1} has to be earlier than {@code date2}.
 */
public static String relativize(Date date1, Date date2) {
    assert date2.getTime() >= date1.getTime();

    long duration = date2.getTime() - date1.getTime();
    long converted;

    if ((converted = TimeUnit.MILLISECONDS.toDays(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "day" : "days");
    } else if ((converted = TimeUnit.MILLISECONDS.toHours(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "hour" : "hours");
    } else if ((converted = TimeUnit.MILLISECONDS.toMinutes(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "minute" : "minutes");
    } else if ((converted = TimeUnit.MILLISECONDS.toSeconds(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "second" : "seconds");
    } else {
        return "just now";
    }
}

Answer 4

jquery.timeago plugin

Jeff, because Stack Overflow uses jQuery extensively, I recommend the jquery.timeago plugin.

Benefits:

• Avoid timestamps dated "1 minute ago" even though the page was opened 10 minutes ago; timeago refreshes automatically.
• You can take full advantage of page and/or fragment caching in your web applications, because the timestamps aren't calculated on the server.
• You get to use microformats like the cool kids.

Just attach it to your timestamps on DOM ready:

jQuery(document).ready(function() {
    jQuery('abbr.timeago').timeago();
});

This will turn all abbr elements with a class of timeago and an ISO 8601 timestamp in the title:

<abbr class="timeago" title="2008-07-17T09:24:17Z">July 17, 2008</abbr>

into something like this:

<abbr class="timeago" title="July 17, 2008">4 months ago</abbr>

which yields: 4 months ago. As time passes, the timestamps will automatically update.

Disclaimer: I wrote this plugin, so I'm biased.

Answer 5

using Fluent DateTime

var dateTime1 = 2.Hours().Ago();
var dateTime2 = 3.Days().Ago();
var dateTime3 = 1.Months().Ago();
var dateTime4 = 5.Hours().FromNow();
var dateTime5 = 2.Weeks().FromNow();
var dateTime6 = 40.Seconds().FromNow();

Answer 6

@Jeff

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

Doing a subtraction on DateTime returns a TimeSpan anyway.

So you can just do

(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?