diff --git a/CHANGELOG_add_trait_monthelable_and_created.md b/CHANGELOG_add_trait_monthelable_and_created.md
index a8f2df5..3f3824a 100644
--- a/CHANGELOG_add_trait_monthelable_and_created.md
+++ b/CHANGELOG_add_trait_monthelable_and_created.md
@@ -1,3 +1,3 @@
 ### Added
-`Entity::CreatableTrait` Trait with creation date
-`Entity::MonthelableTrait` Trait with numeric representation of a month and his numeric year. Useful for statistics purposes.
\ No newline at end of file
+`Entity::CreatableTrait` Trait & interface with creation date
+`Entity::MonthYearTrait` Trait & interface with numeric representation of a month and his numeric year. Useful for statistics purposes.
diff --git a/src/Entity/CreatableInterface.php b/src/Entity/CreatableInterface.php
new file mode 100644
index 0000000..45760d6
--- /dev/null
+++ b/src/Entity/CreatableInterface.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Smart\CoreBundle\Entity;
+
+
+interface CreatableInterface
+{
+    public function getCreatedAt(): ?\DateTime;
+
+    public function setCreatedAt(?\DateTime $createdAt): static;
+}
diff --git a/src/Entity/CreatableTrait.php b/src/Entity/CreatableTrait.php
index c9111e3..2aa7f17 100644
--- a/src/Entity/CreatableTrait.php
+++ b/src/Entity/CreatableTrait.php
@@ -11,7 +11,7 @@ trait CreatableTrait
      * @ORM\Column(name="created_at", type="datetime")
      */
     #[ORM\Column(type: Types::DATETIME_MUTABLE)]
-    private ?\DateTime $createdAt = null;
+    protected ?\DateTime $createdAt = null;
 
     public function getCreatedAt(): ?\DateTime
     {
diff --git a/src/Entity/MonthYearInterface.php b/src/Entity/MonthYearInterface.php
new file mode 100644
index 0000000..0dfc746
--- /dev/null
+++ b/src/Entity/MonthYearInterface.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Smart\CoreBundle\Entity;
+
+interface MonthYearInterface
+{
+    public function getMonth(): int;
+
+    public function setMonth(int $month): void;
+
+    public function getYear(): int;
+
+    public function setYear(int $year): void;
+
+    public function setMonthYearFromDate(\DateTime $date): void;
+
+    public function getFormattedMonth(): string;
+}
diff --git a/src/Entity/MonthelableTrait.php b/src/Entity/MonthYearTrait.php
similarity index 93%
rename from src/Entity/MonthelableTrait.php
rename to src/Entity/MonthYearTrait.php
index 73f5d69..26b19d7 100644
--- a/src/Entity/MonthelableTrait.php
+++ b/src/Entity/MonthYearTrait.php
@@ -6,7 +6,7 @@
 use Smart\CoreBundle\Utils\DateUtils;
 use Symfony\Component\Validator\Constraints as Assert;
 
-trait MonthelableTrait
+trait MonthYearTrait
 {
     /**
      * @ORM\Column(type="integer", nullable=true)
@@ -45,7 +45,7 @@ public function setYear(int $year): void
         $this->year = $year;
     }
 
-    public function setMonthelableDate(\DateTime $date): void
+    public function setMonthYearFromDate(\DateTime $date): void
     {
         $this->month = (int) $date->format('n');
         $this->year = (int) $date->format('Y');