AddingConverter.xaml

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
             x:Class="RelativeTimeSample.Views.MainPage"
             xmlns:converter="clr-namespace:RelativeTimeSample.Helpers"
             Title="News">
    <ContentPage.Resources>
          <ResourceDictionary>
           <converter:RelativeDateTimeConvertor x:Key="RelativeDateTimeConvertor" />
        </ResourceDictionary>
    </ContentPage.Resources>
</ContentPage>