diff --git a/CHANGES.md b/CHANGES.md
index 51b96815..1a5fc849 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+* Apply datetime converter in ItemCollection endpoint model ([#667](https://github.com/stac-utils/stac-fastapi/pull/667))
+
 ## [2.5.2] - 2024-04-19
 
 ### Fixed
diff --git a/stac_fastapi/api/stac_fastapi/api/models.py b/stac_fastapi/api/stac_fastapi/api/models.py
index 53f376aa..c1d70b3c 100644
--- a/stac_fastapi/api/stac_fastapi/api/models.py
+++ b/stac_fastapi/api/stac_fastapi/api/models.py
@@ -16,6 +16,7 @@
     BaseSearchGetRequest,
     BaseSearchPostRequest,
     str2bbox,
+    str_to_interval,
 )
 
 
@@ -127,7 +128,7 @@ class ItemCollectionUri(CollectionUri):
 
     limit: int = attr.ib(default=10)
     bbox: Optional[BBox] = attr.ib(default=None, converter=str2bbox)
-    datetime: Optional[DateTimeType] = attr.ib(default=None)
+    datetime: Optional[DateTimeType] = attr.ib(default=None, converter=str_to_interval)
 
 
 class POSTTokenPagination(BaseModel):