Extensions.ReadableTime.cs

public static string ToReadableTime(this DateTime value)
{
    var ts = new TimeSpan(DateTime.UtcNow.Ticks - value.Ticks);
    double delta = 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";
    }
    var years = Convert.ToInt32(Math.Floor((double)ts.Days / 365));
    return years <= 1 ? "one year ago" : years + " years ago";
}