DateTime Extensions: Display a pretty print of the duration since the original DateTime and Now. For instance: Yesterday, 1min ago. 2weeks, etc.

DateTimeExtensions.cs

using System;

public static class DateTimeExtensions
{
    public static string ToPrettyPast(this DateTime d)
    {
        var timeSpan = DateTime.Now.Subtract(d);

        if (timeSpan.Days == 1)
            return "Yesterday.";
        else if (timeSpan.Days >= 365)
        {
            int years = (int)timeSpan.Days / 365;
            return string.Format("{0} year{1} ago.", years, years > 1 ? "s" : string.Empty);
        }
        else if (timeSpan.Days >= 31)
        {
            int months = (int)timeSpan.Days / 30;
            return string.Format("{0} month{1} ago.", months, months > 1 ? "s" : string.Empty);
        }
        else if (timeSpan.Days > 7 && timeSpan.Days < 31)
        {
            int weeks = (int)timeSpan.Days / 7;
            return string.Format("{0} week{1} ago.", weeks, weeks > 1 ? "s" : string.Empty);
        }
        else if (timeSpan.Days > 0)
            return string.Format("{0} day{1} ago.", timeSpan.Days, timeSpan.Days > 1 ? "s" : string.Empty);
        else if (timeSpan.Hours > 0)
            return string.Format("{0} hour{1} ago.", timeSpan.Hours, timeSpan.Hours > 1 ? "s" : string.Empty);
        else if (timeSpan.Minutes > 0)
            return string.Format("{0} min{1} ago.", timeSpan.Minutes, timeSpan.Minutes > 1 ? "s" : string.Empty);

        return "Just now.";
    }
}

DatetimeExtensionTests.cs

[TestClass]
public class DatetimeExtensionTests
{
    [TestMethod]
    public void Test_Now()
    {
        Assert.AreEqual("Just now.", DateTime.Now.ToPrettyPast());
    }

    [TestMethod]
    public void Test_Miniuts()
    {
        Assert.AreEqual("1 min ago.", DateTime.Now.AddMinutes(-1).ToPrettyPast());
        Assert.AreEqual("2 mins ago.", DateTime.Now.AddMinutes(-2).ToPrettyPast());
    }

    [TestMethod]
    public void Test_Days()
    {
        Assert.AreEqual("Yesterday.", DateTime.Now.AddDays(-1).ToPrettyPast());
        Assert.AreEqual("2 days ago.", DateTime.Now.AddDays(-2).ToPrettyPast());
        Assert.AreEqual("6 days ago.", DateTime.Now.AddDays(-6).ToPrettyPast());
        Assert.AreEqual("7 days ago.", DateTime.Now.AddDays(-7).ToPrettyPast());
    }

    [TestMethod]
    public void Test_Weeks()
    {
        Assert.AreEqual("1 week ago.", DateTime.Now.AddDays(-8).ToPrettyPast());
        Assert.AreEqual("2 weeks ago.", DateTime.Now.AddDays(-15).ToPrettyPast());
        Assert.AreEqual("3 weeks ago.", DateTime.Now.AddDays(-22).ToPrettyPast());
        Assert.AreEqual("4 weeks ago.", DateTime.Now.AddDays(-29).ToPrettyPast());
    }

    [TestMethod]
    public void Test_Month()
    {
        Assert.AreEqual("1 month ago.", DateTime.Now.AddMonths(-1).ToPrettyPast());
        Assert.AreEqual("2 months ago.", DateTime.Now.AddMonths(-2).ToPrettyPast());
        Assert.AreEqual("3 months ago.", DateTime.Now.AddMonths(-3).ToPrettyPast());
        Assert.AreEqual("4 months ago.", DateTime.Now.AddMonths(-4).ToPrettyPast());
        Assert.AreEqual("1 year ago.", DateTime.Now.AddMonths(-12).ToPrettyPast());
    }

    [TestMethod]
    public void Test_Year()
    {
        Assert.AreEqual("1 year ago.", DateTime.Now.AddYears(-1).ToPrettyPast());
        Assert.AreEqual("2 years ago.", DateTime.Now.AddYears(-2).ToPrettyPast());
        Assert.AreEqual("3 years ago.", DateTime.Now.AddYears(-3).ToPrettyPast());
        Assert.AreEqual("4 years ago.", DateTime.Now.AddYears(-4).ToPrettyPast());
    }
}