Develop Reference

Nested parenthesis order of evaluation - Depth vs Ltr

public static float BackInOut(float from, float to, float time)
{
const float s = 1.70158f * 1.525f;
to -= from;
if ((time /= .5f) < 1f)
// 5 6 3 4 0 1 2 7
return to * .5f * (time * time * ((s + 1f) * time - s)) + from;
// 3 0 1 2
return to * .5f * ((time -= 2) * time * ((s + 1f) * time + s) + 2f) + from;
}
In the second return is time used before (and after) being modified? Yes?
// 1 0 2 3
return to * .5f * ((time -= 2) * time * ((s + 1f) * time + s) + 2f) + from;
Or only after, like this? Idk?
Thanks.
source: http://robertpenner.com/easing/
EDIT:
Tried to simplify:
using System;
namespace New_folder
{
class Program
{
static public int s { get; set; } = 2;
static private int _test = 10;
static public int time
{
get
{
Console.WriteLine(_test);
return _test;
}
set { _test = value; }
}
static public void Main(string[] args)
{
var test = (time -= 2) * time * ((s + 1f) * time + s);
}
}
}
This shows:
10
8
8
which shows that my second guess is right and time is only used after modification i think
I guess i was just confused.
It goes into the right branch just to evaluate the deepest nesting then when back on higher level goes back to ltr and does not care where it was duh
thanks

Simplify the example
To answer your question "In the second return is time used before (and after) being modified? Yes?"
How about this?
public int ReturnZeroIfValueIsNegative(int x)
{
if ((x += 100) <= 100) // the "+=" operator changed the value of x
{
return 0;
}
return x; // this will return the altered value of x
}
The above may be re-written to
x = x + 100;
if (x <= 100)
{
return 0;
}
return x;
Order of operations
You could take a look here for a general explanation regarding the order of operations for programming languages.

C# Winforms: Returning values to a button event

I'm completely new to C# programming, and I'm trying to make a custom calculator using Windows Forms.
Three text boxes txtMinSkill, txtMaxSkill, txtCooldown should be keyed values into, and clicking a button buttonCalculate should do some calculations and present the result in a label resultLabel.
I have managed to get everything working down to the skill.Display function, but I have no idea how to display the variables hours, minutes, seconds in the label. When I try to access them from within the button event, I just get a message that it does not exist in the current context. And I can't access the label from the Display method.
Can anyone assist? Thanks!
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void buttonCalculate_Click(object sender, EventArgs e)
{
double minSkill;
double maxSkill;
double coolDown;
minSkill = float.Parse(txtMinSkill.Text) * 10;
maxSkill = float.Parse(txtMaxSkill.Text) * 10;
coolDown = float.Parse(txtCooldown.Text);
SkillGainCalculator skill = new SkillGainCalculator();
skill.IntegerMax(maxSkill);
skill.RemainderMax(maxSkill);
skill.RemainderMin(minSkill);
skill.IntegerMin(minSkill);
skill.Calculate(minSkill,maxSkill);
skill.Display(coolDown);
}
}
class SkillGainCalculator
{
//member variables
private int integerMax;
private int remainderMax;
private int integerMin;
private int remainderMin;
private double counter;
const int constant = 6480;
private int i;
private double totalTime;
private int hours;
private int minutes;
private int seconds;
public double IntegerMax(double intMax)
{
integerMax = (int)((1000 - intMax) / 50);
return integerMax;
}
public int RemainderMax(double intMax)
{
remainderMax = (int)((1000 - intMax) % 50);
return remainderMax;
}
public int RemainderMin(double intMin)
{
remainderMin = (int)((1000 - intMin) % 50);
return remainderMin;
}
public int IntegerMin(double intMin)
{
if (remainderMin == 0)
{
integerMin = (int)((1000 - intMin) / 50) - 1;
return integerMin;
}
else
{
integerMin = (int)((1000 - intMin) / 50);
return integerMin;
}
}
public double Calculate(double intMax, double intMin)
{
for (i = integerMax; i <= integerMin; i++)
{
if (i == integerMax && remainderMax != 0)
{
if (intMax <= 700)
{
counter = counter + constant * Math.Pow(0.8, i) * (50 - remainderMax) / 50;
}
else
{
counter = counter + constant * Math.Pow(0.8, i) * (50 - remainderMax) / 50;
}
}
else if (i == integerMin && remainderMin != 0)
{
if (intMin < 700)
{
counter = counter + constant * Math.Pow(0.8, i) * remainderMin / 50;
}
else
{
counter = counter + constant * Math.Pow(0.8, i) * remainderMin / 50;
}
}
else if (i >= 6)
{
counter = counter + constant * Math.Pow(0.8, i);
}
else
{
counter = counter + constant * Math.Pow(0.8, i);
}
}
return counter;
}
public void Display(double clD)
{
totalTime = counter * clD / 3600;
hours = (int)(counter * clD / 3600);
minutes = (int)((totalTime - hours) * 3600 / 60);
seconds = (int)((totalTime - hours) * 3600 % 60);
}
}

I have no idea, what your code does and as #Steve already said your question misses some key infos. Nevertheless try changing your two methods Display and buttonCalculate_Click like this:
public string Display(double clD)
{
totalTime = counter * clD / 3600;
hours = (int)(counter * clD / 3600);
minutes = (int)((totalTime - hours) * 3600 / 60);
seconds = (int)((totalTime - hours) * 3600 % 60);
return "Hours: " + hours + ", Minutes: " + minutes + ", Seconds: " + seconds;
}
private void buttonCalculate_Click(object sender, EventArgs e)
{
double minSkill;
double maxSkill;
double coolDown;
minSkill = float.Parse(txtMinSkill.Text) * 10;
maxSkill = float.Parse(txtMaxSkill.Text) * 10;
coolDown = float.Parse(txtCooldown.Text);
SkillGainCalculator skill = new SkillGainCalculator();
skill.IntegerMax(maxSkill);
skill.RemainderMax(maxSkill);
skill.RemainderMin(minSkill);
skill.IntegerMin(minSkill);
skill.Calculate(minSkill, maxSkill);
resultLabel.Text = skill.Display(coolDown);
}
The method Display now generates the string you want to display and returns it when called so you can set resultLabel.Text from you calling method:

What is the exact Excel Days360 algorithm?

I'm porting some calculations from Excel to C# which use the Days360 function (the default/US method). Using the Wikipedia page as a guide, I came up with this code:
public static int Days360(DateTime a, DateTime b)
{
var dayA = a.Day;
var dayB = b.Day;
if (IsLastDayOfFebruary(a) && IsLastDayOfFebruary(b))
dayB = 30;
if (dayA == 31 || IsLastDayOfFebruary(a))
dayA = 30;
if (dayA == 30 && dayB == 31)
dayB = 30;
return ((b.Year - a.Year) * 12 + b.Month - a.Month) * 30 + dayB - dayA;
}
private static bool IsLastDayOfFebruary(DateTime date)
{
if (date.Month != 2)
return false;
int lastDay = DateTime.DaysInMonth(date.Year, 2);
return date.Day == lastDay;
}
I tested it with a (small) range of inputs and the results mostly agree with Excel's native function except if I use 2015-02-28 for both a and b. My code returns 0 and Excel -2.
My result seems more reasonable but at this point, I'd prefer to calculate the exact same result as Excel. There might be other inputs where they disagree so I don't want to make a special case just for that date.
Does anyone know the exact algorithm that Excel uses?
EDIT: There was a glaring bug in the original code I posted which is unrelated to the question. I had already fixed that one but I copied from the wrong file when posting the question.

According to this Wikipedia article the Microsoft Excel Days360 function is equivalent to 30/360 BMA/PSA. So to get exact results as MS Excel we need to implement the BMA/PSA method. I have implemented the method.
private double Days360(DateTime StartDate, DateTime EndDate)
{
int StartDay = StartDate.Day;
int StartMonth = StartDate.Month;
int StartYear = StartDate.Year;
int EndDay = EndDate.Day;
int EndMonth = EndDate.Month;
int EndYear = EndDate.Year;
if (StartDay == 31 || IsLastDayOfFebruary(StartDate))
{
StartDay = 30;
}
if (StartDay == 30 && EndDay == 31)
{
EndDay = 30;
}
return ((EndYear - StartYear) * 360) + ((EndMonth - StartMonth) * 30) + (EndDay - StartDay);
}
private bool IsLastDayOfFebruary(DateTime date)
{
return date.Month == 2 && date.Day == DateTime.DaysInMonth(date.Year, date.Month);
}

I had the same need, I found the solution in the function on line 51 of this phpexcel library
dateDiff360
this is part of the class code for the calculation
/**
* Identify if a year is a leap year or not
*
* #param integer $year The year to test
* #return boolean TRUE if the year is a leap year, otherwise FALSE
*/
public static function isLeapYear($year)
{
return ((($year % 4) == 0) && (($year % 100) != 0) || (($year % 400) == 0));
}
/**
* Return the number of days between two dates based on a 360 day calendar
*
* #param integer $startDay Day of month of the start date
* #param integer $startMonth Month of the start date
* #param integer $startYear Year of the start date
* #param integer $endDay Day of month of the start date
* #param integer $endMonth Month of the start date
* #param integer $endYear Year of the start date
* #param boolean $methodUS Whether to use the US method or the European method of calculation
* #return integer Number of days between the start date and the end date
*/
private static function dateDiff360($startDay, $startMonth, $startYear, $endDay, $endMonth, $endYear, $methodUS)
{
if ($startDay == 31) {
--$startDay;
} elseif ($methodUS && ($startMonth == 2 && ($startDay == 29 || ($startDay == 28 && !self::isLeapYear($startYear))))) {
$startDay = 30;
}
if ($endDay == 31) {
if ($methodUS && $startDay != 30) {
$endDay = 1;
if ($endMonth == 12) {
++$endYear;
$endMonth = 1;
} else {
++$endMonth;
}
} else {
$endDay = 30;
}
}
return $endDay + $endMonth * 30 + $endYear * 360 - $startDay - $startMonth * 30 - $startYear * 360;
}

This algorithm also include the optional parameter method:
int startMonthDays = 0;
int endMonthDays = 0;
double diff = 0;
if(method.Equals("TRUE"))
{
if(dtStartDate.getDay() < 30)
{
startMonthDays = (30 - dtStartDate.getDay());
}
else
{
startMonthDays = 0;
}
if(dtEndDate.getDay() < 30)
{
endMonthDays = dtEndDate.getDay();
}
else
{
endMonthDays = 30;
}
diff = (dtEndDate.getYear() - dtStartDate.getYear())*360 +
(dtEndDate.getMonth() - dtStartDate.getMonth() - 1)*30 +
startMonthDays + endMonthDays;
}
else
{
if(DateCalendar.daysInMonth(dtStartDate.getYear(), dtStartDate.getMonth()) == dtStartDate.getDay())
{
startMonthDays = 0;
}
else
{
startMonthDays = (30 - dtStartDate.getDay());
}
if(DateCalendar.daysInMonth(dtEndDate.getYear(), dtEndDate.getMonth()) == dtEndDate.getDay())
{
if(dtStartDate.getDay() < DateCalendar.daysInMonth(dtStartDate.getYear(), dtStartDate.getMonth()) - 1)
{
if(DateCalendar.daysInMonth(dtEndDate.getYear(), dtEndDate.getMonth()) > 30)
{
endMonthDays = DateCalendar.daysInMonth(dtEndDate.getYear(), dtEndDate.getMonth());
}
else
{
endMonthDays = dtEndDate.getDay();
}
}
else
{
if(DateCalendar.daysInMonth(dtEndDate.getYear(), dtEndDate.getMonth()) > 30)
{
endMonthDays = DateCalendar.daysInMonth(dtEndDate.getYear(), dtEndDate.getMonth()) - 1;
}
else
{
endMonthDays = dtEndDate.getDay();
}
}
}
else
{
endMonthDays = dtEndDate.getDay();
}
diff = (dtEndDate.getYear() - dtStartDate.getYear())*360 +
(dtEndDate.getMonth() - dtStartDate.getMonth() - 1)*30 +
startMonthDays + endMonthDays;
}
with
public static int daysInMonth (int year, int month)
{
if (DateTime.IsLeapYear(year) && month == 2)
{
return 29;
}
else
{
return table[month - 1];
}
}
and
private static readonly int[] table = new int[]{ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

Test the next
public static int Days360(DateTime a, DateTime b)
{
var dayA = a.Day;
var dayB = b.Day;
if (IsLastDayOfMonth(a) && IsLastDayOfMonth(b)) {
dayB = Math.min(30, dayB);
} else if (dayA == 30 && dayB ==31) {
DayB = 30;
}
if (IsLastDayOfMonth(a))
dayA = 30;
return ((b.Year - a.Year) * 360 + b.Month - a.Month) * 30 + dayB - dayA;
}
private static bool IsLastDayOfMonth(DateTime date)
{
int lastDay = DateTime.DaysInMonth(date.Year, date.Month);
return date.Day == lastDay;
}

String terminator for converting Time Strings [duplicate]

This question already has answers here:
Calculate relative time in C#
(41 answers)
Closed 9 years ago.
I have a String Array like
First[i]
In this array, the values are Like
"00hr:00min:17sec"
"00hr:03min:18sec"
"00hr:05min:25sec"
"01hr:39min:44sec"
Now I take another string array like
Secound[j]
"17sec Ago"
"3min Ago"
"5min Ago"
"1hr Ago"
How can I convert first string array to seconds string array?

parse the string into components; possibly by position, possibly with Parse, possibly with regex
decide what rules you want for each output
use it
For example:
static string SimplifyTime(string value)
{
var match = Regex.Match(value, "([0-9]{2})hr:([0-9]{2})min:([0-9]{2})sec");
if (!match.Success) return value;
int val = int.Parse(match.Groups[1].Value, CultureInfo.InvariantCulture);
if (val > 0) return val + "hr Ago";
val = int.Parse(match.Groups[2].Value, CultureInfo.InvariantCulture);
if (val > 0) return val + "min Ago";
val = int.Parse(match.Groups[3].Value, CultureInfo.InvariantCulture);
return val + "sec Ago";
}
static void Main()
{
string[] values = {
"00hr:00min:17sec",
"00hr:03min:18sec",
"00hr:05min:25sec",
"01hr:39min:44sec"
};
var converted = Array.ConvertAll(values, SimplifyTime);
}

string[] first ={"00hr:00min:17sec",
"00hr:03min:18sec",
"00hr:05min:25sec",
"01hr:39min:44sec"};
string[] second = new string[first.Length];
string pattern = #"([0-9]{2})hr:([0-9]{2})min:([0-9]{2})sec";
for (int i = 0; i < first.Length; i++)
{
Match match = Regex.Match(first[i],pattern);
if (match.Success)
{
int hour = int.Parse(match.Groups[1].Value);
if (hour > 0)
second[i] = hour + "hr ago";
else
{
int min = int.Parse(match.Groups[2].Value);
if (min > 0)
second[i] = min + "min ago";
else
{
int sec = int.Parse(match.Groups[3].Value);
if (sec > 0)
second[i] = sec + "sec ago";
}
}
}
}
you will using System.Text.RegularExpressions;

First you need to convert it to a TimeSpan:
string[] strTimeSpans = new[]{"00hr:00min:17sec","00hr:03min:18sec","00hr:05min:25sec","01hr:39min:44sec"};
TimeSpan[] timespans = strTimeSpans
.Select(s => {
var parts = s.Split(':');
int hour = int.Parse(parts[0].Substring(0, 2));
int min = int.Parse(parts[1].Substring(0, 2));
int sec = int.Parse(parts[2].Substring(0, 2));
return new TimeSpan(hour, min, sec);
}).ToArray();
Then you can use this code to get a readable TimeSpan, i have added it to a method:
public static string GetReadableTimespan(TimeSpan ts)
{
const int SECOND = 1;
const int MINUTE = 60 * SECOND;
const int HOUR = 60 * MINUTE;
const int DAY = 24 * HOUR;
const int MONTH = 30 * DAY;
double delta = Math.Abs(ts.TotalSeconds);
if (delta < 0)
{
return "not yet";
}
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";
}
}
Now this....
foreach (TimeSpan ts in timespans)
Console.WriteLine(GetReadableTimespan(ts));
outputs:
17 seconds ago
3 minutes ago
5 minutes ago
1 hours ago
Demo

I believe that the regularal expression answers are better and more professional. But i also post another approach more amatuer.
string[] First = new string[] { "00hr:00min:17sec",
"00hr:03min:18sec",
"00hr:05min:25sec",
"01hr:39min:44sec"};
string[] Secound = new string[First.Length];
for(int i =0 ;i<First.Length;i++)
{
string hour = First[i].Split(':')[0].Replace("hr", "");
string min = First[i].Split(':')[1].Replace("min", "");
string sec = First[i].Split(':')[2].Replace("sec", "");
if (Convert.ToInt32(hour) > 0)
{
hour = hour + "hr Ago";
Secound[i] = hour;
continue;
}
if (Convert.ToInt32(min) > 0)
{
min = min + "min Ago";
Secound[i] = min;
continue;
}
if (Convert.ToInt32(sec) > 0)
{
sec = sec + "sec Ago";
Secound[i] = sec;
continue;
}
}

Calculate relative time in C#

Given a specific DateTime value, how do I display relative time, like:
2 hours ago
3 days ago
a month ago

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";
}

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.

Here's how I do it
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 < 60 * 2)
{
return "a minute ago";
}
if (delta < 45 * 60)
{
return ts.Minutes + " minutes ago";
}
if (delta < 90 * 60)
{
return "an hour ago";
}
if (delta < 24 * 60 * 60)
{
return ts.Hours + " hours ago";
}
if (delta < 48 * 60 * 60)
{
return "yesterday";
}
if (delta < 30 * 24 * 60 * 60)
{
return ts.Days + " days ago";
}
if (delta < 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?

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

Here a rewrite from Jeffs Script for PHP:
define("SECOND", 1);
define("MINUTE", 60 * SECOND);
define("HOUR", 60 * MINUTE);
define("DAY", 24 * HOUR);
define("MONTH", 30 * DAY);
function relativeTime($time)
{
$delta = time() - $time;
if ($delta < 1 * MINUTE)
{
return $delta == 1 ? "one second ago" : $delta . " seconds ago";
}
if ($delta < 2 * MINUTE)
{
return "a minute ago";
}
if ($delta < 45 * MINUTE)
{
return floor($delta / MINUTE) . " minutes ago";
}
if ($delta < 90 * MINUTE)
{
return "an hour ago";
}
if ($delta < 24 * HOUR)
{
return floor($delta / HOUR) . " hours ago";
}
if ($delta < 48 * HOUR)
{
return "yesterday";
}
if ($delta < 30 * DAY)
{
return floor($delta / DAY) . " days ago";
}
if ($delta < 12 * MONTH)
{
$months = floor($delta / DAY / 30);
return $months <= 1 ? "one month ago" : $months . " months ago";
}
else
{
$years = floor($delta / DAY / 365);
return $years <= 1 ? "one year ago" : $years . " years ago";
}
}

public static string ToRelativeDate(DateTime input)
{
TimeSpan oSpan = DateTime.Now.Subtract(input);
double TotalMinutes = oSpan.TotalMinutes;
string Suffix = " ago";
if (TotalMinutes < 0.0)
{
TotalMinutes = Math.Abs(TotalMinutes);
Suffix = " from now";
}
var aValue = new SortedList<double, Func<string>>();
aValue.Add(0.75, () => "less than a minute");
aValue.Add(1.5, () => "about a minute");
aValue.Add(45, () => string.Format("{0} minutes", Math.Round(TotalMinutes)));
aValue.Add(90, () => "about an hour");
aValue.Add(1440, () => string.Format("about {0} hours", Math.Round(Math.Abs(oSpan.TotalHours)))); // 60 * 24
aValue.Add(2880, () => "a day"); // 60 * 48
aValue.Add(43200, () => string.Format("{0} days", Math.Floor(Math.Abs(oSpan.TotalDays)))); // 60 * 24 * 30
aValue.Add(86400, () => "about a month"); // 60 * 24 * 60
aValue.Add(525600, () => string.Format("{0} months", Math.Floor(Math.Abs(oSpan.TotalDays / 30)))); // 60 * 24 * 365
aValue.Add(1051200, () => "about a year"); // 60 * 24 * 365 * 2
aValue.Add(double.MaxValue, () => string.Format("{0} years", Math.Floor(Math.Abs(oSpan.TotalDays / 365))));
return aValue.First(n => TotalMinutes < n.Key).Value.Invoke() + Suffix;
}
http://refactormycode.com/codes/493-twitter-esque-relative-dates
C# 6 version:
static readonly SortedList<double, Func<TimeSpan, string>> offsets =
new SortedList<double, Func<TimeSpan, string>>
{
{ 0.75, _ => "less than a minute"},
{ 1.5, _ => "about a minute"},
{ 45, x => $"{x.TotalMinutes:F0} minutes"},
{ 90, x => "about an hour"},
{ 1440, x => $"about {x.TotalHours:F0} hours"},
{ 2880, x => "a day"},
{ 43200, x => $"{x.TotalDays:F0} days"},
{ 86400, x => "about a month"},
{ 525600, x => $"{x.TotalDays / 30:F0} months"},
{ 1051200, x => "about a year"},
{ double.MaxValue, x => $"{x.TotalDays / 365:F0} years"}
};
public static string ToRelativeDate(this DateTime input)
{
TimeSpan x = DateTime.Now - input;
string Suffix = x.TotalMinutes > 0 ? " ago" : " from now";
x = new TimeSpan(Math.Abs(x.Ticks));
return offsets.First(n => x.TotalMinutes < n.Key).Value(x) + Suffix;
}

Here's an implementation I added as an extension method to the DateTime class that handles both future and past dates and provides an approximation option that allows you to specify the level of detail you're looking for ("3 hour ago" vs "3 hours, 23 minutes, 12 seconds ago"):
using System.Text;
/// <summary>
/// Compares a supplied date to the current date and generates a friendly English
/// comparison ("5 days ago", "5 days from now")
/// </summary>
/// <param name="date">The date to convert</param>
/// <param name="approximate">When off, calculate timespan down to the second.
/// When on, approximate to the largest round unit of time.</param>
/// <returns></returns>
public static string ToRelativeDateString(this DateTime value, bool approximate)
{
StringBuilder sb = new StringBuilder();
string suffix = (value > DateTime.Now) ? " from now" : " ago";
TimeSpan timeSpan = new TimeSpan(Math.Abs(DateTime.Now.Subtract(value).Ticks));
if (timeSpan.Days > 0)
{
sb.AppendFormat("{0} {1}", timeSpan.Days,
(timeSpan.Days > 1) ? "days" : "day");
if (approximate) return sb.ToString() + suffix;
}
if (timeSpan.Hours > 0)
{
sb.AppendFormat("{0}{1} {2}", (sb.Length > 0) ? ", " : string.Empty,
timeSpan.Hours, (timeSpan.Hours > 1) ? "hours" : "hour");
if (approximate) return sb.ToString() + suffix;
}
if (timeSpan.Minutes > 0)
{
sb.AppendFormat("{0}{1} {2}", (sb.Length > 0) ? ", " : string.Empty,
timeSpan.Minutes, (timeSpan.Minutes > 1) ? "minutes" : "minute");
if (approximate) return sb.ToString() + suffix;
}
if (timeSpan.Seconds > 0)
{
sb.AppendFormat("{0}{1} {2}", (sb.Length > 0) ? ", " : string.Empty,
timeSpan.Seconds, (timeSpan.Seconds > 1) ? "seconds" : "second");
if (approximate) return sb.ToString() + suffix;
}
if (sb.Length == 0) return "right now";
sb.Append(suffix);
return sb.ToString();
}

There are also a package called Humanizr on Nuget, and it actually works really well, and is in the .NET Foundation.
DateTime.UtcNow.AddHours(-30).Humanize() => "yesterday"
DateTime.UtcNow.AddHours(-2).Humanize() => "2 hours ago"
DateTime.UtcNow.AddHours(30).Humanize() => "tomorrow"
DateTime.UtcNow.AddHours(2).Humanize() => "2 hours from now"
TimeSpan.FromMilliseconds(1299630020).Humanize() => "2 weeks"
TimeSpan.FromMilliseconds(1299630020).Humanize(3) => "2 weeks, 1 day, 1 hour"
Scott Hanselman has a writeup on it on his blog

I would recommend computing this on the client side too. Less work for the server.
The following is the version that I use (from Zach Leatherman)
/*
* Javascript Humane Dates
* Copyright (c) 2008 Dean Landolt (deanlandolt.com)
* Re-write by Zach Leatherman (zachleat.com)
*
* Adopted from the John Resig's pretty.js
* at http://ejohn.org/blog/javascript-pretty-date
* and henrah's proposed modification
* at http://ejohn.org/blog/javascript-pretty-date/#comment-297458
*
* Licensed under the MIT license.
*/
function humane_date(date_str){
var time_formats = [
[60, 'just now'],
[90, '1 minute'], // 60*1.5
[3600, 'minutes', 60], // 60*60, 60
[5400, '1 hour'], // 60*60*1.5
[86400, 'hours', 3600], // 60*60*24, 60*60
[129600, '1 day'], // 60*60*24*1.5
[604800, 'days', 86400], // 60*60*24*7, 60*60*24
[907200, '1 week'], // 60*60*24*7*1.5
[2628000, 'weeks', 604800], // 60*60*24*(365/12), 60*60*24*7
[3942000, '1 month'], // 60*60*24*(365/12)*1.5
[31536000, 'months', 2628000], // 60*60*24*365, 60*60*24*(365/12)
[47304000, '1 year'], // 60*60*24*365*1.5
[3153600000, 'years', 31536000], // 60*60*24*365*100, 60*60*24*365
[4730400000, '1 century'] // 60*60*24*365*100*1.5
];
var time = ('' + date_str).replace(/-/g,"/").replace(/[TZ]/g," "),
dt = new Date,
seconds = ((dt - new Date(time) + (dt.getTimezoneOffset() * 60000)) / 1000),
token = ' ago',
i = 0,
format;
if (seconds < 0) {
seconds = Math.abs(seconds);
token = '';
}
while (format = time_formats[i++]) {
if (seconds < format[0]) {
if (format.length == 2) {
return format[1] + (i > 1 ? token : ''); // Conditional so we don't return Just Now Ago
} else {
return Math.round(seconds / format[2]) + ' ' + format[1] + (i > 1 ? token : '');
}
}
}
// overflow for centuries
if(seconds > 4730400000)
return Math.round(seconds / 4730400000) + ' centuries' + token;
return date_str;
};
if(typeof jQuery != 'undefined') {
jQuery.fn.humane_dates = function(){
return this.each(function(){
var date = humane_date(this.title);
if(date && jQuery(this).text() != date) // don't modify the dom if we don't have to
jQuery(this).text(date);
});
};
}

#jeff
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, I usually elect to keep this short and simple.
This is the method I am currently using in one of my websites. This returns only a relative day, hour and time. And then the user has to slap on "ago" in the output.
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();
}

A couple of years late to the party, but I had a requirement to do this for both past and future dates, so I combined Jeff's and Vincent's into this. It's a ternarytastic extravaganza! :)
public static class DateTimeHelper
{
private const int SECOND = 1;
private const int MINUTE = 60 * SECOND;
private const int HOUR = 60 * MINUTE;
private const int DAY = 24 * HOUR;
private const int MONTH = 30 * DAY;
/// <summary>
/// Returns a friendly version of the provided DateTime, relative to now. E.g.: "2 days ago", or "in 6 months".
/// </summary>
/// <param name="dateTime">The DateTime to compare to Now</param>
/// <returns>A friendly string</returns>
public static string GetFriendlyRelativeTime(DateTime dateTime)
{
if (DateTime.UtcNow.Ticks == dateTime.Ticks)
{
return "Right now!";
}
bool isFuture = (DateTime.UtcNow.Ticks < dateTime.Ticks);
var ts = DateTime.UtcNow.Ticks < dateTime.Ticks ? new TimeSpan(dateTime.Ticks - DateTime.UtcNow.Ticks) : new TimeSpan(DateTime.UtcNow.Ticks - dateTime.Ticks);
double delta = ts.TotalSeconds;
if (delta < 1 * MINUTE)
{
return isFuture ? "in " + (ts.Seconds == 1 ? "one second" : ts.Seconds + " seconds") : ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago";
}
if (delta < 2 * MINUTE)
{
return isFuture ? "in a minute" : "a minute ago";
}
if (delta < 45 * MINUTE)
{
return isFuture ? "in " + ts.Minutes + " minutes" : ts.Minutes + " minutes ago";
}
if (delta < 90 * MINUTE)
{
return isFuture ? "in an hour" : "an hour ago";
}
if (delta < 24 * HOUR)
{
return isFuture ? "in " + ts.Hours + " hours" : ts.Hours + " hours ago";
}
if (delta < 48 * HOUR)
{
return isFuture ? "tomorrow" : "yesterday";
}
if (delta < 30 * DAY)
{
return isFuture ? "in " + ts.Days + " days" : ts.Days + " days ago";
}
if (delta < 12 * MONTH)
{
int months = Convert.ToInt32(Math.Floor((double)ts.Days / 30));
return isFuture ? "in " + (months <= 1 ? "one month" : months + " months") : months <= 1 ? "one month ago" : months + " months ago";
}
else
{
int years = Convert.ToInt32(Math.Floor((double)ts.Days / 365));
return isFuture ? "in " + (years <= 1 ? "one year" : years + " years") : years <= 1 ? "one year ago" : years + " years ago";
}
}
}

Given the world and her husband appear to be posting code samples, here is what I wrote a while ago, based on a couple of these answers.
I had a specific need for this code to be localisable. So I have two classes — Grammar, which specifies the localisable terms, and FuzzyDateExtensions, which holds a bunch of extension methods. I had no need to deal with future datetimes, so no attempt is made to handle them with this code.
I've left some of the XMLdoc in the source, but removed most (where they'd be obvious) for brevity's sake. I've also not included every class member here:
public class Grammar
{
/// <summary> Gets or sets the term for "just now". </summary>
public string JustNow { get; set; }
/// <summary> Gets or sets the term for "X minutes ago". </summary>
/// <remarks>
/// This is a <see cref="String.Format"/> pattern, where <c>{0}</c>
/// is the number of minutes.
/// </remarks>
public string MinutesAgo { get; set; }
public string OneHourAgo { get; set; }
public string HoursAgo { get; set; }
public string Yesterday { get; set; }
public string DaysAgo { get; set; }
public string LastMonth { get; set; }
public string MonthsAgo { get; set; }
public string LastYear { get; set; }
public string YearsAgo { get; set; }
/// <summary> Gets or sets the term for "ages ago". </summary>
public string AgesAgo { get; set; }
/// <summary>
/// Gets or sets the threshold beyond which the fuzzy date should be
/// considered "ages ago".
/// </summary>
public TimeSpan AgesAgoThreshold { get; set; }
/// <summary>
/// Initialises a new <see cref="Grammar"/> instance with the
/// specified properties.
/// </summary>
private void Initialise(string justNow, string minutesAgo,
string oneHourAgo, string hoursAgo, string yesterday, string daysAgo,
string lastMonth, string monthsAgo, string lastYear, string yearsAgo,
string agesAgo, TimeSpan agesAgoThreshold)
{ ... }
}
The FuzzyDateString class contains:
public static class FuzzyDateExtensions
{
public static string ToFuzzyDateString(this TimeSpan timespan)
{
return timespan.ToFuzzyDateString(new Grammar());
}
public static string ToFuzzyDateString(this TimeSpan timespan,
Grammar grammar)
{
return GetFuzzyDateString(timespan, grammar);
}
public static string ToFuzzyDateString(this DateTime datetime)
{
return (DateTime.Now - datetime).ToFuzzyDateString();
}
public static string ToFuzzyDateString(this DateTime datetime,
Grammar grammar)
{
return (DateTime.Now - datetime).ToFuzzyDateString(grammar);
}
private static string GetFuzzyDateString(TimeSpan timespan,
Grammar grammar)
{
timespan = timespan.Duration();
if (timespan >= grammar.AgesAgoThreshold)
{
return grammar.AgesAgo;
}
if (timespan < new TimeSpan(0, 2, 0)) // 2 minutes
{
return grammar.JustNow;
}
if (timespan < new TimeSpan(1, 0, 0)) // 1 hour
{
return String.Format(grammar.MinutesAgo, timespan.Minutes);
}
if (timespan < new TimeSpan(1, 55, 0)) // 1 hour 55 minutes
{
return grammar.OneHourAgo;
}
if (timespan < new TimeSpan(12, 0, 0) // 12 hours
&& (DateTime.Now - timespan).IsToday())
{
return String.Format(grammar.HoursAgo, timespan.RoundedHours());
}
if ((DateTime.Now.AddDays(1) - timespan).IsToday())
{
return grammar.Yesterday;
}
if (timespan < new TimeSpan(32, 0, 0, 0) // 32 days
&& (DateTime.Now - timespan).IsThisMonth())
{
return String.Format(grammar.DaysAgo, timespan.RoundedDays());
}
if ((DateTime.Now.AddMonths(1) - timespan).IsThisMonth())
{
return grammar.LastMonth;
}
if (timespan < new TimeSpan(365, 0, 0, 0, 0) // 365 days
&& (DateTime.Now - timespan).IsThisYear())
{
return String.Format(grammar.MonthsAgo, timespan.RoundedMonths());
}
if ((DateTime.Now - timespan).AddYears(1).IsThisYear())
{
return grammar.LastYear;
}
return String.Format(grammar.YearsAgo, timespan.RoundedYears());
}
}
One of the key things I wanted to achieve, as well as localisation, was that "today" would only mean "this calendar day", so the IsToday, IsThisMonth, IsThisYear methods look like this:
public static bool IsToday(this DateTime date)
{
return date.DayOfYear == DateTime.Now.DayOfYear && date.IsThisYear();
}
and the rounding methods are like this (I've included RoundedMonths, as that's a bit different):
public static int RoundedDays(this TimeSpan timespan)
{
return (timespan.Hours > 12) ? timespan.Days + 1 : timespan.Days;
}
public static int RoundedMonths(this TimeSpan timespan)
{
DateTime then = DateTime.Now - timespan;
// Number of partial months elapsed since 1 Jan, AD 1 (DateTime.MinValue)
int nowMonthYears = DateTime.Now.Year * 12 + DateTime.Now.Month;
int thenMonthYears = then.Year * 12 + then.Month;
return nowMonthYears - thenMonthYears;
}
I hope people find this useful and/or interesting :o)

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();

Is there an easy way to do this in Java? The java.util.Date class seems rather limited.
Here is my quick and dirty Java solution:
import java.util.Date;
import javax.management.timer.Timer;
String getRelativeDate(Date date) {
long delta = new Date().getTime() - date.getTime();
if (delta < 1L * Timer.ONE_MINUTE) {
return toSeconds(delta) == 1 ? "one second ago" : toSeconds(delta) + " seconds ago";
}
if (delta < 2L * Timer.ONE_MINUTE) {
return "a minute ago";
}
if (delta < 45L * Timer.ONE_MINUTE) {
return toMinutes(delta) + " minutes ago";
}
if (delta < 90L * Timer.ONE_MINUTE) {
return "an hour ago";
}
if (delta < 24L * Timer.ONE_HOUR) {
return toHours(delta) + " hours ago";
}
if (delta < 48L * Timer.ONE_HOUR) {
return "yesterday";
}
if (delta < 30L * Timer.ONE_DAY) {
return toDays(delta) + " days ago";
}
if (delta < 12L * 4L * Timer.ONE_WEEK) { // a month
long months = toMonths(delta);
return months <= 1 ? "one month ago" : months + " months ago";
}
else {
long years = toYears(delta);
return years <= 1 ? "one year ago" : years + " years ago";
}
}
private long toSeconds(long date) {
return date / 1000L;
}
private long toMinutes(long date) {
return toSeconds(date) / 60L;
}
private long toHours(long date) {
return toMinutes(date) / 60L;
}
private long toDays(long date) {
return toHours(date) / 24L;
}
private long toMonths(long date) {
return toDays(date) / 30L;
}
private long toYears(long date) {
return toMonths(date) / 365L;
}

iPhone Objective-C Version
+ (NSString *)timeAgoString:(NSDate *)date {
int delta = -(int)[date timeIntervalSinceNow];
if (delta < 60)
{
return delta == 1 ? #"one second ago" : [NSString stringWithFormat:#"%i seconds ago", delta];
}
if (delta < 120)
{
return #"a minute ago";
}
if (delta < 2700)
{
return [NSString stringWithFormat:#"%i minutes ago", delta/60];
}
if (delta < 5400)
{
return #"an hour ago";
}
if (delta < 24 * 3600)
{
return [NSString stringWithFormat:#"%i hours ago", delta/3600];
}
if (delta < 48 * 3600)
{
return #"yesterday";
}
if (delta < 30 * 24 * 3600)
{
return [NSString stringWithFormat:#"%i days ago", delta/(24*3600)];
}
if (delta < 12 * 30 * 24 * 3600)
{
int months = delta/(30*24*3600);
return months <= 1 ? #"one month ago" : [NSString stringWithFormat:#"%i months ago", months];
}
else
{
int years = delta/(12*30*24*3600);
return years <= 1 ? #"one year ago" : [NSString stringWithFormat:#"%i years ago", years];
}
}

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

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

using System;
using System.Collections.Generic;
using System.Linq;
public static class RelativeDateHelper
{
private static Dictionary<double, Func<double, string>> sm_Dict = null;
private static Dictionary<double, Func<double, string>> DictionarySetup()
{
var dict = new Dictionary<double, Func<double, string>>();
dict.Add(0.75, (mins) => "less than a minute");
dict.Add(1.5, (mins) => "about a minute");
dict.Add(45, (mins) => string.Format("{0} minutes", Math.Round(mins)));
dict.Add(90, (mins) => "about an hour");
dict.Add(1440, (mins) => string.Format("about {0} hours", Math.Round(Math.Abs(mins / 60)))); // 60 * 24
dict.Add(2880, (mins) => "a day"); // 60 * 48
dict.Add(43200, (mins) => string.Format("{0} days", Math.Floor(Math.Abs(mins / 1440)))); // 60 * 24 * 30
dict.Add(86400, (mins) => "about a month"); // 60 * 24 * 60
dict.Add(525600, (mins) => string.Format("{0} months", Math.Floor(Math.Abs(mins / 43200)))); // 60 * 24 * 365
dict.Add(1051200, (mins) => "about a year"); // 60 * 24 * 365 * 2
dict.Add(double.MaxValue, (mins) => string.Format("{0} years", Math.Floor(Math.Abs(mins / 525600))));
return dict;
}
public static string ToRelativeDate(this DateTime input)
{
TimeSpan oSpan = DateTime.Now.Subtract(input);
double TotalMinutes = oSpan.TotalMinutes;
string Suffix = " ago";
if (TotalMinutes < 0.0)
{
TotalMinutes = Math.Abs(TotalMinutes);
Suffix = " from now";
}
if (null == sm_Dict)
sm_Dict = DictionarySetup();
return sm_Dict.First(n => TotalMinutes < n.Key).Value.Invoke(TotalMinutes) + Suffix;
}
}
The same as another answer to this question but as an extension method with a static dictionary.

In PHP, I do it this way:
<?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";
} ?>

you can try this.I think it will work correctly.
long delta = new Date().getTime() - date.getTime();
const int SECOND = 1;
const int MINUTE = 60 * SECOND;
const int HOUR = 60 * MINUTE;
const int DAY = 24 * HOUR;
const int MONTH = 30 * DAY;
if (delta < 0L)
{
return "not yet";
}
if (delta < 1L * MINUTE)
{
return ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago";
}
if (delta < 2L * MINUTE)
{
return "a minute ago";
}
if (delta < 45L * MINUTE)
{
return ts.Minutes + " minutes ago";
}
if (delta < 90L * MINUTE)
{
return "an hour ago";
}
if (delta < 24L * HOUR)
{
return ts.Hours + " hours ago";
}
if (delta < 48L * HOUR)
{
return "yesterday";
}
if (delta < 30L * DAY)
{
return ts.Days + " days ago";
}
if (delta < 12L * 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";
}

#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?

You can use TimeAgo extension as below:
public static string TimeAgo(this DateTime dateTime)
{
string result = string.Empty;
var timeSpan = DateTime.Now.Subtract(dateTime);
if (timeSpan <= TimeSpan.FromSeconds(60))
{
result = string.Format("{0} seconds ago", timeSpan.Seconds);
}
else if (timeSpan <= TimeSpan.FromMinutes(60))
{
result = timeSpan.Minutes > 1 ?
String.Format("about {0} minutes ago", timeSpan.Minutes) :
"about a minute ago";
}
else if (timeSpan <= TimeSpan.FromHours(24))
{
result = timeSpan.Hours > 1 ?
String.Format("about {0} hours ago", timeSpan.Hours) :
"about an hour ago";
}
else if (timeSpan <= TimeSpan.FromDays(30))
{
result = timeSpan.Days > 1 ?
String.Format("about {0} days ago", timeSpan.Days) :
"yesterday";
}
else if (timeSpan <= TimeSpan.FromDays(365))
{
result = timeSpan.Days > 30 ?
String.Format("about {0} months ago", timeSpan.Days / 30) :
"about a month ago";
}
else
{
result = timeSpan.Days > 365 ?
String.Format("about {0} years ago", timeSpan.Days / 365) :
"about a year ago";
}
return result;
}
Or use jQuery plugin with Razor extension from Timeago.

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:
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().

Here's the algorithm stackoverflow uses but rewritten more concisely in perlish pseudocode with a bug fix (no "one hours ago"). The function takes a (positive) number of seconds ago and returns a human-friendly string like "3 hours ago" or "yesterday".
agoify($delta)
local($y, $mo, $d, $h, $m, $s);
$s = floor($delta);
if($s<=1) return "a second ago";
if($s<60) return "$s seconds ago";
$m = floor($s/60);
if($m==1) return "a minute ago";
if($m<45) return "$m minutes ago";
$h = floor($m/60);
if($h==1) return "an hour ago";
if($h<24) return "$h hours ago";
$d = floor($h/24);
if($d<2) return "yesterday";
if($d<30) return "$d days ago";
$mo = floor($d/30);
if($mo<=1) return "a month ago";
$y = floor($mo/12);
if($y<1) return "$mo months ago";
if($y==1) return "a year ago";
return "$y years ago";

I got this answer from one of Bill Gates' blogs. I need to find it on my browser history and I'll give you the link.
The Javascript code to do the same thing (as requested):
function posted(t) {
var now = new Date();
var diff = parseInt((now.getTime() - Date.parse(t)) / 1000);
if (diff < 60) { return 'less than a minute ago'; }
else if (diff < 120) { return 'about a minute ago'; }
else if (diff < (2700)) { return (parseInt(diff / 60)).toString() + ' minutes ago'; }
else if (diff < (5400)) { return 'about an hour ago'; }
else if (diff < (86400)) { return 'about ' + (parseInt(diff / 3600)).toString() + ' hours ago'; }
else if (diff < (172800)) { return '1 day ago'; }
else {return (parseInt(diff / 86400)).toString() + ' days ago'; }
}
Basically, you work in terms of seconds.

Java for client-side gwt usage:
import java.util.Date;
public class RelativeDateFormat {
private static final long ONE_MINUTE = 60000L;
private static final long ONE_HOUR = 3600000L;
private static final long ONE_DAY = 86400000L;
private static final long ONE_WEEK = 604800000L;
public static String format(Date date) {
long delta = new Date().getTime() - date.getTime();
if (delta < 1L * ONE_MINUTE) {
return toSeconds(delta) == 1 ? "one second ago" : toSeconds(delta)
+ " seconds ago";
}
if (delta < 2L * ONE_MINUTE) {
return "one minute ago";
}
if (delta < 45L * ONE_MINUTE) {
return toMinutes(delta) + " minutes ago";
}
if (delta < 90L * ONE_MINUTE) {
return "one hour ago";
}
if (delta < 24L * ONE_HOUR) {
return toHours(delta) + " hours ago";
}
if (delta < 48L * ONE_HOUR) {
return "yesterday";
}
if (delta < 30L * ONE_DAY) {
return toDays(delta) + " days ago";
}
if (delta < 12L * 4L * ONE_WEEK) {
long months = toMonths(delta);
return months <= 1 ? "one month ago" : months + " months ago";
} else {
long years = toYears(delta);
return years <= 1 ? "one year ago" : years + " years ago";
}
}
private static long toSeconds(long date) {
return date / 1000L;
}
private static long toMinutes(long date) {
return toSeconds(date) / 60L;
}
private static long toHours(long date) {
return toMinutes(date) / 60L;
}
private static long toDays(long date) {
return toHours(date) / 24L;
}
private static long toMonths(long date) {
return toDays(date) / 30L;
}
private static long toYears(long date) {
return toMonths(date) / 365L;
}
}

I think there is already a number of answers related to this post, but one can use this which is easy to use just like plugin and also easily readable for programmers.
Send your specific date, and get its value in string form:
public string RelativeDateTimeCount(DateTime inputDateTime)
{
string outputDateTime = string.Empty;
TimeSpan ts = DateTime.Now - inputDateTime;
if (ts.Days > 7)
{ outputDateTime = inputDateTime.ToString("MMMM d, yyyy"); }
else if (ts.Days > 0)
{
outputDateTime = ts.Days == 1 ? ("about 1 Day ago") : ("about " + ts.Days.ToString() + " Days ago");
}
else if (ts.Hours > 0)
{
outputDateTime = ts.Hours == 1 ? ("an hour ago") : (ts.Hours.ToString() + " hours ago");
}
else if (ts.Minutes > 0)
{
outputDateTime = ts.Minutes == 1 ? ("1 minute ago") : (ts.Minutes.ToString() + " minutes ago");
}
else outputDateTime = "few seconds ago";
return outputDateTime;
}

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

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...

I would provide some handy extensions methods for this and make the code more readable. First, couple of extension methods for Int32.
public static class TimeSpanExtensions {
public static TimeSpan Days(this int value) {
return new TimeSpan(value, 0, 0, 0);
}
public static TimeSpan Hours(this int value) {
return new TimeSpan(0, value, 0, 0);
}
public static TimeSpan Minutes(this int value) {
return new TimeSpan(0, 0, value, 0);
}
public static TimeSpan Seconds(this int value) {
return new TimeSpan(0, 0, 0, value);
}
public static TimeSpan Milliseconds(this int value) {
return new TimeSpan(0, 0, 0, 0, value);
}
public static DateTime Ago(this TimeSpan value) {
return DateTime.Now - value;
}
}
Then, one for DateTime.
public static class DateTimeExtensions {
public static DateTime Ago(this DateTime dateTime, TimeSpan delta) {
return dateTime - delta;
}
}
Now, you can do something like below:
var date = DateTime.Now;
date.Ago(2.Days()); // 2 days ago
date.Ago(7.Hours()); // 7 hours ago
date.Ago(567.Milliseconds()); // 567 milliseconds ago