## Bug description
 
It looks like either timestamp or sent_at is being sent without timezone, causing [this issue](https://sentry.io/organizations/posthog/issues/1972106098/?project=1899813&query=is%3Aunresolved&statsPeriod=14d)

## Expected behavior

It should send both timestamps with timezone

## How to reproduce

1. 
2. 
3. 

## Environment

- PostHog cloud or self-managed?
- PostHog version/commit

## Additional context



#### *Thank you* for your bug report – we love squashing them!

ee/clickhouse/process_event.py
session_id=properties["$session_id"],
                snapshot_data=properties["$snapshot_data"],
                timestamp=ts,
            )
            return
        _capture_ee(
            event_uuid=event_uuid,
            person_uuid=person_uuid,
            ip=ip,
            site_url=site_url,
            team_id=team_id,
            event=data["event"],
            distinct_id=distinct_id,
            properties=properties,
            timestamp=ts,
        )
        timer.stop("process_event_ee")
else:
    def process_event_ee(
        distinct_id: str,
        ip: str,
        site_url: str,
        data: dict,
        team_id: int,
        now: datetime.datetime,
        sent_at: Optional[datetime.datetime],
    ) -> None:
        
        return
def log_event(