diff --git a/src/ionbeam/aggregators/by_time_2.py b/src/ionbeam/aggregators/by_time_2.py
index 7ff120d..6fd6291 100644
--- a/src/ionbeam/aggregators/by_time_2.py
+++ b/src/ionbeam/aggregators/by_time_2.py
@@ -12,7 +12,7 @@
 import logging
 from collections import defaultdict
 from dataclasses import field
-from datetime import datetime, time, timedelta, timezone
+from datetime import datetime, time, timedelta
 from typing import Iterable, Literal
 
 import pandas as pd
@@ -29,6 +29,7 @@
 @dataclasses.dataclass
 class NewTimeAggregator(Aggregator):
     "How much time a data granule represents."
+
     granularity_hours: int = 1
 
     "Is data arriving chronologically or the reverse?"
@@ -67,32 +68,44 @@ def init(self, globals):
 
     def bucket_to_message(self, bucket):
         data = [m.data for m in bucket]
+        print(data)
         return TabularMessage(
             metadata=self.metadata,
             data=pd.concat(data),
         )
 
     def update_time_frontier(self, start_time, end_time):
-        assert start_time.tzinfo is not None
-        assert end_time.tzinfo is not None
+        if start_time.tzinfo is not None:
+            start_time = start_time.tz_convert("UTC").tz_localize(None)
+        if end_time.tzinfo is not None:
+            end_time = end_time.tz_convert("UTC").tz_localize(None)
 
         if self.time_frontier is None:
-            self.time_frontier = start_time if self.time_direction == "forwards" else end_time
+            self.time_frontier = (
+                start_time if self.time_direction == "forwards" else end_time
+            )
             return
         if self.time_direction == "forwards":
             self.time_frontier = max(self.time_frontier, start_time)
         elif self.time_direction == "backwards":
             self.time_frontier = min(self.time_frontier, end_time)
 
-    def process(self, message: TabularMessage | FinishMessage) -> Iterable[TabularMessage]:
+    def process(
+        self, message: TabularMessage | FinishMessage
+    ) -> Iterable[TabularMessage]:
         if isinstance(message, FinishMessage):
             for _, bucket in self.time_chunks.items():
                 yield self.bucket_to_message(bucket)
             return
 
         message_timedelta = message.data.time.max() - message.data.time.min()
-        self.min_emit_after_hours = max(self.min_emit_after_hours, message_timedelta.total_seconds() / 60**2)
-        self.update_time_frontier(start_time=message.data.time.min(), end_time=message.data.time.max())
+        self.min_emit_after_hours = max(
+            self.min_emit_after_hours, message_timedelta.total_seconds() / 60**2
+        )
+        self.update_time_frontier(
+            start_time=message.data.time.min(),
+            end_time=message.data.time.max(),
+        )
 
         print(
             f"""
@@ -107,11 +120,13 @@ def process(self, message: TabularMessage | FinishMessage) -> Iterable[TabularMe
 
         # convert timezone to utc and convert to time naive
         message.data.time = message.data.time.dt.tz_convert("UTC").dt.tz_localize(None)
-        for (date, hour), data_chunk in message.data.groupby([message.data.time.dt.date, message.data.time.dt.hour]):
+        for (date, hour), data_chunk in message.data.groupby(
+            [message.data.time.dt.date, message.data.time.dt.hour]
+        ):
             if data_chunk.empty:
                 continue
             chunked_message = dataclasses.replace(message, data=data_chunk)
-            start_time = datetime.combine(date, time(hour=hour, tzinfo=timezone.utc))
+            start_time = datetime.combine(date, time(hour=hour, tzinfo=None))
             self.time_chunks[start_time].append(chunked_message)
 
         assert self.time_frontier is not None