diff --git a/CHANGES.md b/CHANGES.md
index f60e95f9..940b7b84 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,11 +1,15 @@
 # Changelog
 
-[Unreleased] - TBD
+## [Unreleased] - TBD
 
-## Changed
+### Changed
+
+* switch from `fastapi` to `fastapi-slim` to avoid installing unwanted dependencies. ([#687](https://github.com/stac-utils/stac-fastapi/pull/687))
+* replace Enum with `Literal` for `FilterLang`. ([#686](https://github.com/stac-utils/stac-fastapi/pull/686))
+
+### Removed
 
-* switch from `fastapi` to `fastapi-slim` to avoid installing unwanted dependencies
-* replace Enum with `Literal` for `FilterLang`
+* Pystac as it was just used for a datetime to string function. ([#690](https://github.com/stac-utils/stac-fastapi/pull/690))
 
 ## [3.0.0a0] - 2024-05-06
 
diff --git a/stac_fastapi/types/stac_fastapi/types/rfc3339.py b/stac_fastapi/types/stac_fastapi/types/rfc3339.py
index d5ded8d9..fc3ab8a9 100644
--- a/stac_fastapi/types/stac_fastapi/types/rfc3339.py
+++ b/stac_fastapi/types/stac_fastapi/types/rfc3339.py
@@ -20,14 +20,13 @@
 ]
 
 
+# Borrowed from pystac - https://github.com/stac-utils/pystac/blob/main/pystac/utils.py#L370C1-L394C21
 def datetime_to_str(dt: datetime, timespec: str = "auto") -> str:
     """Converts a :class:`datetime.datetime` instance to an ISO8601 string in the
     `RFC 3339, section 5.6
     <https://datatracker.ietf.org/doc/html/rfc3339#section-5.6>`__ format required by
     the :stac-spec:`STAC Spec <master/item-spec/common-metadata.md#date-and-time>`.
 
-    Borrowed from pystac - https://github.com/stac-utils/pystac/blob/main/pystac/utils.py#L370C1-L394C21
-
     Args:
         dt : The datetime to convert.
         timespec: An optional argument that specifies the number of additional