A Real Timespan Object With .Years & .Months

Here is the main answer with code, please note that you can get any number of dates/times accuracy, seconds & minutes, or seconds, minutes and days, anywhere up to years (which would contain 6 parts/segments). If you specify top two and it's over a year old, it will return "1 year and 3 months ago" and won't return the rest because you've requested two segments. if it's only a few hours old, then it will only return "2 hours and 1 minute ago". Of course, same rules apply if you specify 1, 2, 3, 4, 5 or 6 segmets (maxes out at 6 because seconds, minutes, hours, days, months, years only make 6 types). It will also correct grammer issues like "minutes" vs "minute" depending on if it's 1 minute or more, same for all types, and the "string" generated will always be grammatically correct.

Here are some examples for use: bAllowSegments identifies how many segments to show... ie: if 3, then return string would be (as an example)... "3 years, 2 months and 13 days" (won't include hours, minutes and seconds as the top 3 time categories are returned), if however, the date was a newer date, such as something a few days ago, specifying the same segments (3) will return "4 days, 1 hour and 13 minutes ago" instead, so it takes everything into account!

if bAllowSegments is 2 it would return "3 years and 2 months" and if 6 (maximum value) would return "3 years, 2 months, 13 days, 13 hours, 29 minutes and 9 seconds", but, be reminded that it will NEVER RETURN something like this "0 years, 0 months, 0 days, 3 hours, 2 minutes and 13 seconds ago" as it understands there is no date data in the top 3 segments and ignores them, even if you specify 6 segments, so don't worry :). Of course, if there is a segment with 0 in it, it will take that into account when forming the string, and will display as "3 days and 4 seconds ago" and ignoring the "0 hours" part! Enjoy and please comment if you like.

 Public Function RealTimeUntilNow(ByVal dt As DateTime, Optional ByVal bAllowSegments As Byte = 2) As String
  ' bAllowSegments identifies how many segments to show... ie: if 3, then return string would be (as an example)...
  ' "3 years, 2 months and 13 days" the top 3 time categories are returned, if bAllowSegments is 2 it would return
  ' "3 years and 2 months" and if 6 (maximum value) would return "3 years, 2 months, 13 days, 13 hours, 29 minutes and 9 seconds"
  Dim rYears, rMonths, rDays, rHours, rMinutes, rSeconds As Int16
  Dim dtNow = DateTime.Now
  Dim daysInBaseMonth = Date.DaysInMonth(dt.Year, dt.Month)

  rYears = dtNow.Year - dt.Year
  rMonths = dtNow.Month - dt.Month
  If rMonths < 0 Then rMonths += 12 : rYears -= 1 ' add 1 year to months, and remove 1 year from years.
  rDays = dtNow.Day - dt.Day
  If rDays < 0 Then rDays += daysInBaseMonth : rMonths -= 1
  rHours = dtNow.Hour - dt.Hour
  If rHours < 0 Then rHours += 24 : rDays -= 1
  rMinutes = dtNow.Minute - dt.Minute
  If rMinutes < 0 Then rMinutes += 60 : rHours -= 1
  rSeconds = dtNow.Second - dt.Second
  If rSeconds < 0 Then rSeconds += 60 : rMinutes -= 1

  ' this is the display functionality
  Dim sb As StringBuilder = New StringBuilder()
  Dim iSegmentsAdded As Int16 = 0

  If rYears > 0 Then sb.Append(rYears) : sb.Append(" year" & If(rYears <> 1, "s", "") & ", ") : iSegmentsAdded += 1
  If bAllowSegments = iSegmentsAdded Then GoTo parseAndReturn

  If rMonths > 0 Then sb.AppendFormat(rMonths) : sb.Append(" month" & If(rMonths <> 1, "s", "") & ", ") : iSegmentsAdded += 1
  If bAllowSegments = iSegmentsAdded Then GoTo parseAndReturn

  If rDays > 0 Then sb.Append(rDays) : sb.Append(" day" & If(rDays <> 1, "s", "") & ", ") : iSegmentsAdded += 1
  If bAllowSegments = iSegmentsAdded Then GoTo parseAndReturn

  If rHours > 0 Then sb.Append(rHours) : sb.Append(" hour" & If(rHours <> 1, "s", "") & ", ") : iSegmentsAdded += 1
  If bAllowSegments = iSegmentsAdded Then GoTo parseAndReturn

  If rMinutes > 0 Then sb.Append(rMinutes) : sb.Append(" minute" & If(rMinutes <> 1, "s", "") & ", ") : iSegmentsAdded += 1
  If bAllowSegments = iSegmentsAdded Then GoTo parseAndReturn

  If rSeconds > 0 Then sb.Append(rSeconds) : sb.Append(" second" & If(rSeconds <> 1, "s", "") & "") : iSegmentsAdded += 1

parseAndReturn:

  ' if the string is entirely empty, that means it was just posted so its less than a second ago, and an empty string getting passed will cause an error
  ' so we construct our own meaningful string which will still fit into the "Posted * ago " syntax...

  If sb.ToString = "" Then sb.Append("less than 1 second")

  Return ReplaceLast(sb.ToString.TrimEnd(" ", ",").ToString, ",", " and")

 End Function

Of course, you will need a "ReplaceLast" function, which takes a source string, and an argument specifying what needs to be replaced, and another arg specifying what you want to replace it with, and it only replaces the last occurance of that string... i've included my one if you don't have one or dont want to implement it, so here it is, it will work "as is" with no modification needed. I know the reverseit function is no longer needed (exists in .net) but the ReplaceLast and the ReverseIt func are carried over from the pre-.net days, so please excuse how dated it may look (still works 100% tho, been using em for over ten years, can guarante they are bug free)... :). Also, if you are using VB6, you can use StrReverse (wrapping it around the string extended with the .ReverseIt extension method), instead of using the ReverseIt() function (provided as an extension method). So, instead of doing sReplacable.ReverseIt, you'd do StrReverse(sReplacable) as StrReverse() is a built in VB6 function (and does the exact same thing, reverses a given string, and does nothing more). If you use StrReverse() instead of my generic ReverseIt function, feel free to delete the ReverseIt function/extension. StrReverse() function should be available in .NET as long as you are importing the legacy ms-visualbasic-dll library. Makes no difference either way, I had written ReverseIt() before I even know a StrReverse() function had existed, and had been using it ever since out of habit (no real reason to use mine as opposed to the in-built generic function StrReverse) - in fact, I'm sure StrReverse (or a similar, newer .NET specific version of a string reversing function) would be written to be more efficient :). cheers.

<Extension()> _ 
Public Function ReplaceLast(ByVal sReplacable As String, ByVal sReplaceWhat As String, ByVal sReplaceWith As String) As String 
    ' let empty string arguments run, incase we dont know if we are sending and empty string or not. 
    sReplacable = sReplacable.ReverseIt 
    sReplacable = Replace(sReplacable, sReplaceWhat.ReverseIt, sReplaceWith.ReverseIt, , 1) ' only does first item on reversed version! 
    Return sReplacable.ReverseIt.ToString 
End Function 

<Extension()> _ 
Public Function ReverseIt(ByVal strS As String, Optional ByVal n As Integer = -1) As String 
    Dim strTempX As String = "", intI As Integer 

    If n > strS.Length Or n = -1 Then n = strS.Length 

    For intI = n To 1 Step -1 
        strTempX = strTempX + Mid(strS, intI, 1) 
    Next intI 

    ReverseIt = strTempX + Right(strS, Len(strS) - n) 

End Function 

Well, better late then nothing I suppose ;)

C# function giving everything

And this is my modified version :

private string GetElapsedTime(DateTime from_date, DateTime to_date) {
int years;
int months;
int days;
int hours;
int minutes;
int seconds;
int milliseconds;

//------------------
// Handle the years.
//------------------
years = to_date.Year - from_date.Year;

//------------------------
// See if we went too far.
//------------------------
DateTime test_date = from_date.AddMonths(12 * years);

if (test_date > to_date)
{
    years--;
    test_date = from_date.AddMonths(12 * years);
}

//--------------------------------
// Add months until we go too far.
//--------------------------------
months = 0;

while (test_date <= to_date)
{
    months++;
    test_date = from_date.AddMonths(12 * years + months);
}

months--;

//------------------------------------------------------------------
// Subtract to see how many more days, hours, minutes, etc. we need.
//------------------------------------------------------------------
from_date = from_date.AddMonths(12 * years + months);
TimeSpan remainder = to_date - from_date;
days = remainder.Days;
hours = remainder.Hours;
minutes = remainder.Minutes;
seconds = remainder.Seconds;
milliseconds = remainder.Milliseconds;

return (years > 0 ? years.ToString() + " years " : "") +
       (months > 0 ? months.ToString() + " months " : "") +
       (days > 0 ? days.ToString() + " days " : "") +
       (hours > 0 ? hours.ToString() + " hours " : "") +
       (minutes > 0 ? minutes.ToString() + " minutes " : "");}

What you are looking for is indeed not what TimeSpan represents. TimeSpan represents an interval as a count of ticks, without respect to a base DateTime or Calendar.

A new DateDifference type might make more sense here, with a constructor or factory method taking a base DateTime, a target DateTime, and optionally a Calendar (defaulting to CultureInfo.CurrentCulture) with which to compute the various difference components (years, months, etc.)

EDIT: It looks to me like Noda Time may have the tools you need for this — the Period class "[r]epresents a period of time expressed in human chronological terms: hours, days, weeks, months and so on", and in particular Period.Between(then, now, PeriodUnits.AllUnits) seems to be the precise calculation you're asking for — but it's necessarily a much more complex class than TimeSpan. The Key Concepts page on the Noda Time wiki explains how "humans make time messy":

Leaving aside the tricky bits of astronomy and relativity, mankind has still made time hard to negotiate. If we all used ticks from the Unix epoch to talk about time, there wouldn't be a need for a library like Noda Time.

But no, we like to talk in years, months, days, weeks - and for some reason we like 12pm (which confusingly comes before 1pm) to be roughly the time at which the sun is highest... so we have time zones.

Not only that, but we don't all agree on how many months there are. Different civilizations have come up with different ways of splitting up the year, and different numbers for the years to start with. These are calendar systems.

Here's how to add some extension methods for this with C# using mean values:

public static class TimeSpanExtensions
{
    public static int GetYears(this TimeSpan timespan)
    {
        return (int)(timespan.Days/365.2425);
    }
    public static int GetMonths(this TimeSpan timespan)
    {
        return (int)(timespan.Days/30.436875);
    }
}