Time travel in Rails? Yes. Timecop does exactly that, and boy is it fun to use. Here’s how I quickly made a date picker that allows to modify Time.zone.now and test different processes.

1. Install Timecop

   bundle add timecop
   

2. Create a date selector form. Bonus: add a sprinkle of JS so that the form submits itself each time we pick a date.

   <%= form_with(url: set_date_path, id:'global-date') do |form| %>
     <%= form.date_field :global_date, id:'date-input', placeholder: Time.zone.now.strftime('%d/%m/%Y') %>
   <% end %>
   <script>
     document.addEventListener("turbo:load", function() {
       const dateInput = document.getElementById("date-input");
       dateInput.addEventListener("change", function() {
         document.getElementById("global-date").submit();
       });
     });
   </script>
   

3. Create the set_date method in your ApplicationController using Timecop

   def set_date
     Timecop.travel(params[:global_date])
     redirect_back(fallback_location: root_path, notice: t("notices.global_date", global_date: Time.zone.now.strftime('%d/%m/%Y')))
   end
   

4. Add the route for setting the date

   patch '/set_date', to: 'application#set_date', as: 'set_date'
   

And voilà, you are now equiped with a tool that H. G. Wells could only dream of.