diff --git a/api/app/v1/endpoints/read/query_parameters.py b/api/app/v1/endpoints/read/query_parameters.py
index 09c59d5..86e4c72 100644
--- a/api/app/v1/endpoints/read/query_parameters.py
+++ b/api/app/v1/endpoints/read/query_parameters.py
@@ -12,8 +12,60 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from datetime import datetime, timezone
+
 from app import VERSIONING
-from fastapi import Depends, Query
+from dateutil.parser import isoparse
+from fastapi import Depends, HTTPException, Query, status
+
+
+def _validation_error(message):
+    return HTTPException(
+        status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+        detail={
+            "code": 422,
+            "type": "error",
+            "message": message,
+        },
+    )
+
+
+def _parse_iso_datetime(value, parameter_name):
+    try:
+        parsed = isoparse(value)
+    except (TypeError, ValueError) as exc:
+        raise _validation_error(
+            f"Invalid {parameter_name}: expected an ISO 8601 datetime"
+        ) from exc
+
+    if parsed.tzinfo is None:
+        parsed = parsed.replace(tzinfo=datetime.now().astimezone().tzinfo)
+
+    return parsed.astimezone(timezone.utc)
+
+
+def _validate_time_travel_params(as_of, from_to):
+    if as_of and from_to:
+        raise _validation_error("$as_of and $from_to cannot be used together")
+
+    if as_of:
+        as_of_value = _parse_iso_datetime(as_of, "$as_of")
+        if as_of_value > datetime.now(timezone.utc):
+            raise _validation_error("$as_of value cannot be in the future")
+
+    if from_to:
+        values = from_to.split("/", 1)
+        if len(values) != 2 or not values[0] or not values[1]:
+            raise _validation_error(
+                "Invalid $from_to: expected format is $from_to=<start>/<end>"
+            )
+
+        start = _parse_iso_datetime(values[0], "$from_to start")
+        end = _parse_iso_datetime(values[1], "$from_to end")
+        if start > end:
+            raise _validation_error(
+                "$from_to start cannot be greater than $from_to end"
+            )
 
 
 class CommonQueryParams:
@@ -73,6 +125,7 @@ def __init__(
         self.filter = filter
         self.as_of = as_of
         self.from_to = from_to
+        _validate_time_travel_params(as_of, from_to)
 
 
 def get_common_query_params(
diff --git a/test/unit/test_query_parameters.py b/test/unit/test_query_parameters.py
new file mode 100644
index 0000000..c95e907
--- /dev/null
+++ b/test/unit/test_query_parameters.py
@@ -0,0 +1,79 @@
+from datetime import datetime, timedelta, timezone
+
+import pytest
+from fastapi import HTTPException
+
+from app.v1.endpoints.read.query_parameters import CommonQueryParams
+
+
+def _future_datetime():
+    return (datetime.now(timezone.utc) + timedelta(days=1)).isoformat().replace(
+        "+00:00", "Z"
+    )
+
+
+def test_common_query_params_accepts_valid_as_of():
+    params = CommonQueryParams(as_of="2024-01-01T00:00:00Z")
+
+    assert params.as_of == "2024-01-01T00:00:00Z"
+
+
+def test_common_query_params_rejects_invalid_as_of():
+    with pytest.raises(HTTPException) as exc_info:
+        CommonQueryParams(as_of="not-a-date")
+
+    assert exc_info.value.status_code == 422
+    assert "$as_of" in exc_info.value.detail["message"]
+
+
+def test_common_query_params_rejects_future_as_of():
+    with pytest.raises(HTTPException) as exc_info:
+        CommonQueryParams(as_of=_future_datetime())
+
+    assert exc_info.value.status_code == 422
+    assert "future" in exc_info.value.detail["message"]
+
+
+def test_common_query_params_accepts_valid_from_to():
+    params = CommonQueryParams(
+        from_to="2024-01-01T00:00:00Z/2024-01-02T00:00:00Z"
+    )
+
+    assert params.from_to == "2024-01-01T00:00:00Z/2024-01-02T00:00:00Z"
+
+
+@pytest.mark.parametrize(
+    "from_to",
+    [
+        "2024-01-01T00:00:00Z",
+        "/2024-01-02T00:00:00Z",
+        "2024-01-01T00:00:00Z/",
+        "not-a-date/2024-01-02T00:00:00Z",
+    ],
+)
+def test_common_query_params_rejects_invalid_from_to(from_to):
+    with pytest.raises(HTTPException) as exc_info:
+        CommonQueryParams(from_to=from_to)
+
+    assert exc_info.value.status_code == 422
+
+
+def test_common_query_params_rejects_reversed_from_to():
+    with pytest.raises(HTTPException) as exc_info:
+        CommonQueryParams(
+            from_to="2024-01-02T00:00:00Z/2024-01-01T00:00:00Z"
+        )
+
+    assert exc_info.value.status_code == 422
+    assert "greater" in exc_info.value.detail["message"]
+
+
+def test_common_query_params_rejects_as_of_with_from_to():
+    with pytest.raises(HTTPException) as exc_info:
+        CommonQueryParams(
+            as_of="2024-01-01T00:00:00Z",
+            from_to="2024-01-01T00:00:00Z/2024-01-02T00:00:00Z",
+        )
+
+    assert exc_info.value.status_code == 422
+    assert "cannot be used together" in exc_info.value.detail["message"]