diff --git a/edc_consent/consent_definition.py b/edc_consent/consent_definition.py
index 6bbe0b3..7854d4c 100644
--- a/edc_consent/consent_definition.py
+++ b/edc_consent/consent_definition.py
@@ -69,8 +69,12 @@ def __post_init__(self):
             raise ConsentDefinitionError(f"Invalid gender. Got {self.gender}.")
         if not self.start.tzinfo:
             raise ConsentDefinitionError(f"Naive datetime not allowed. Got {self.start}.")
+        elif str(self.start.tzinfo) != "UTC":
+            raise ConsentDefinitionError(f"Start date must be UTC. Got {self.start}.")
         if not self.end.tzinfo:
             raise ConsentDefinitionError(f"Naive datetime not allowed Got {self.end}.")
+        elif str(self.end.tzinfo) != "UTC":
+            raise ConsentDefinitionError(f"End date must be UTC. Got {self.end}.")
         self.check_date_within_study_period()
 
     @property
diff --git a/edc_consent/site_consents.py b/edc_consent/site_consents.py
index b5ccdb9..84b0ff6 100644
--- a/edc_consent/site_consents.py
+++ b/edc_consent/site_consents.py
@@ -9,7 +9,7 @@
 from django.core.management.color import color_style
 from django.utils.module_loading import import_module, module_has_submodule
 from edc_sites.site import sites as site_sites
-from edc_utils import ceil_secs, floor_secs, formatted_date
+from edc_utils import ceil_secs, floor_secs, formatted_date, to_utc
 
 from .exceptions import (
     AlreadyRegistered,
@@ -141,7 +141,7 @@ def get_consent_or_raise(
             subject_identifier=subject_identifier,
             raise_if_not_consented=raise_if_not_consented,
         )
-        if consent_obj and report_datetime < consent_obj.consent_datetime:
+        if consent_obj and to_utc(report_datetime) < consent_obj.consent_datetime:
             if not cdef.updates:
                 dte = formatted_date(report_datetime)
                 raise ConsentDefinitionNotConfiguredForUpdate(
@@ -257,7 +257,7 @@ def _filter_cdefs_by_report_datetime_or_raise(
             cdefs = [
                 cdef
                 for cdef in cdefs
-                if floor_secs(cdef.start) <= report_datetime <= ceil_secs(cdef.end)
+                if floor_secs(cdef.start) <= to_utc(report_datetime) <= ceil_secs(cdef.end)
             ]
             if not cdefs:
                 date_string = formatted_date(report_datetime)