Replicate moment.js fromNow() and toNow() in C#

Question

I tried to ask this question but some users thought it was a duplicate and closed the question. I explained it in a comment but in any case, I wrote an extension method in C# and it will appear in an answer.

Answer 1

Here is the extension for replicating moment.js fromNow() and toNow(). It's useful if some of your pages are server generated (e.g. Razor view engine) and you want the same time ago verbiage.

public static class Extensions
{
    // For from_now and to_now
    static Dictionary<string, string> relative_time = new Dictionary<string, string>()
    {
        { "future" , "in {0}" },
        { "past" , "in {0}" },
        { "s" , "a few seconds ago" },
        { "m" , "a minute ago" },
        { "mm" , "{0} minutes ago" },
        { "h" , "an hour ago" },
        { "hh" , "{0} hours ago" },
        { "d" , "a day ago" },
        { "dd" , "{0} days ago" },
        { "M" , "a month ago" },
        { "MM" , "{0} months ago" },
        { "Y" , "a year ago" },
        { "YY" , "{0} years ago" },
        { "-s" , "in seconds" },
        { "-m" , "in a minute" },
        { "-mm" , "in {0} minutes" },
        { "-h" , "in an hour" },
        { "-hh" , "in {0} hours" },
        { "-d" , "in a day" },
        { "-dd" , "in {0} days" },
        { "-M" , "in a month" },
        { "-MM" , "in {0} months" },
        { "-Y" , "in a year" },
        { "-YY" , "in {0} years" },
    };

    /// <summary>
    /// replicate moment.js fromNow()
    /// </summary>
    /// <returns></returns>
    public static string from_now(this DateTime time_gmt)
    {
        // http://momentjs.com/docs/#/displaying/fromnow  : moment.js fromNow() doc

        var diff = DateTime.UtcNow - time_gmt;
        if (diff.TotalSeconds < 0)
        {
            return time_gmt.to_now();
        }
        else if (diff.TotalSeconds <= 45)
        {
            return relative_time["s"];
        }
        else if (diff.TotalSeconds <= 90)
        {
            return relative_time["m"];
        }
        else if (diff.TotalMinutes <= 45)
        {
            return string.Format(relative_time["mm"], Convert.ToInt32( diff.TotalMinutes));
        }
        else if (diff.TotalMinutes <= 90)
        {
            return relative_time["h"];
        }
        else if (diff.TotalHours <= 22)
        {
            return string.Format(relative_time["hh"], Convert.ToInt32(diff.TotalHours));
        }
        else if (diff.TotalHours <= 36)
        {
            return relative_time["d"];
        }
        else if (diff.TotalDays <= 25)
        {
            return string.Format(relative_time["dd"], Convert.ToInt32(diff.TotalDays));
        }
        else if (diff.TotalDays <= 45)
        {
            return relative_time["M"];
        }
        else if (diff.TotalDays <= 345)
        {
            return string.Format(relative_time["MM"], Convert.ToInt32(diff.TotalDays/(365.0/12.0)));
        }
        else if (diff.TotalDays <= 545)
        {
            return relative_time["Y"];
        }
        else if (diff.TotalDays > 545)
        {
            return string.Format(relative_time["YY"], Convert.ToInt32(diff.TotalDays/365.0));
        }
        return "invalid";
    }

    /// <summary>
    /// replicate moment.js toNow()
    /// </summary>
    /// <param name="time_gmt"></param>
    /// <returns></returns>
    public static string to_now(this DateTime time_gmt)
    {
        // http://momentjs.com/docs/#/displaying/tonow  : moment.js toNow() doc

        var diff = time_gmt - DateTime.UtcNow;
        if (diff.TotalSeconds < 0)
        {
            return time_gmt.from_now();
        }
        else if (diff.TotalSeconds <= 45)
        {
            return relative_time["-s"];
        }
        else if (diff.TotalSeconds <= 90)
        {
            return relative_time["-m"];
        }
        else if (diff.TotalMinutes <= 45)
        {
            return string.Format(relative_time["-mm"], Convert.ToInt32( diff.TotalMinutes));
        }
        else if (diff.TotalMinutes <= 90)
        {
            return relative_time["-h"];
        }
        else if (diff.TotalHours <= 22)
        {
            return string.Format(relative_time["-hh"], Convert.ToInt32(diff.TotalHours));
        }
        else if (diff.TotalHours <= 36)
        {
            return relative_time["-d"];
        }
        else if (diff.TotalDays <= 25)
        {
            return string.Format(relative_time["-dd"], Convert.ToInt32(diff.TotalDays));
        }
        else if (diff.TotalDays <= 45)
        {
            return relative_time["-M"];
        }
        else if (diff.TotalDays <= 345)
        {
            return string.Format(relative_time["-MM"], Convert.ToInt32(diff.TotalDays/(365.0/12.0)));
        }
        else if (diff.TotalDays <= 545)
        {
            return relative_time["-Y"];
        }
        else if (diff.TotalDays > 545)
        {
            return string.Format(relative_time["-YY"], Convert.ToInt32(diff.TotalDays/365.0));
        }
        return "invalid";
    }
}