diff --git a/test/support/helpers.ex b/test/support/helpers.ex
index 0cfae90..fba72dc 100644
--- a/test/support/helpers.ex
+++ b/test/support/helpers.ex
@@ -2,7 +2,7 @@ defmodule DecentralisedBookIndex.Helpers do
   @moduledoc "Helpers for tests"
 
   @doc """
-  Rerurn a new map with same keys as in map_with_keys.
+  Return a new map with same keys as in map_with_keys.
   """
   def get_submap(map, map_with_keys) when is_map(map_with_keys) do
     Map.take(map, Map.keys(map_with_keys))
@@ -17,4 +17,27 @@ defmodule DecentralisedBookIndex.Helpers do
       get_submap(map, keys)
     end)
   end
+
+  def datetime_from_iso_8601(datetime_string) do
+    case DateTime.from_iso8601(datetime_string) do
+      {:ok, datetime, 0} -> datetime
+      _ -> nil
+    end
+  end
+
+  @doc """
+  Return a new map with updated keys :inserted_at and :updated_at.
+  Those keys will be transformed from string to DateTime.
+  """
+  def datetime_from_iso8601_for_map(map) do
+    map
+    |> Map.update(:inserted_at, nil, &datetime_from_iso_8601/1)
+    |> Map.update(:updated_at, nil, &datetime_from_iso_8601/1)
+  end
+
+  def datetime_add_second_as_string(datetime, seconds) do
+    datetime
+    |> DateTime.add(seconds)
+    |> DateTime.to_iso8601()
+  end
 end