Updated DateTime types.

src/Entity/RoomPrice.php

@@ -38,9 +38,9 @@ class RoomPrice
         return $this;
     }
 
-    public function getDate(): ?\DateTime
+    public function getDate(): ?\DateTimeImmutable
     {
-        return new \DateTime($this->date);
+        return new \DateTimeImmutable($this->date);
     }
 
     public function getDateString(): ?string
@@ -48,7 +48,7 @@ class RoomPrice
         return $this->date;
     }
 
-    public function setDate(\DateTime $date): static
+    public function setDate(\DateTimeInterface $date): static
     {
         $this->date = $date->format('Y-m-d');