Timeago razor helper for asp.net core

timeago.cs

// Razor 
// -------------------------------------------------------------------
<timeago>@comment.UtcCreatedDateTime</timeago>

// Helper 
// -------------------------------------------------------------------
using Microsoft.AspNetCore.Razor.TagHelpers;
using System;
using System.Threading.Tasks;

namespace Wiyf.Web.Common.AuthoringTagHelpers
{
    public class TimeagoTagHelper : TagHelper
    {
        public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
        {
            output.TagName = "span";
            var result = string.Empty;
            var content = await output.GetChildContentAsync();

            if (DateTime.TryParse(content.GetContent(), out var dateTime))
            {
                var timeSpan = DateTime.UtcNow.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("{0} minutes ago", timeSpan.Minutes) :
                        "a minute ago";
                }
                else if (timeSpan <= TimeSpan.FromHours(24))
                {
                    result = timeSpan.Hours > 1 ?
                        string.Format("{0} hours ago", timeSpan.Hours) :
                        "an hour ago";
                }
                else if (timeSpan <= TimeSpan.FromDays(30))
                {
                    result = timeSpan.Days > 1 ?
                        string.Format("{0} days ago", timeSpan.Days) :
                        "yesterday";
                }
                else if (timeSpan <= TimeSpan.FromDays(365))
                {
                    result = timeSpan.Days > 30 ?
                        string.Format("{0} months ago", timeSpan.Days / 30) :
                        "a month ago";
                }
                else
                {
                    result = timeSpan.Days > 365 ?
                        string.Format("{0} years ago", timeSpan.Days / 365) :
                        "a year ago";
                }
            }

            output.Content.SetContent(result);
        }
    }
}