## Bug description

When I create a fairly simple query (event + 1 filter) and click on the graph to open the person models (sep 3), I get 25 people, whereas the graph says there should be 17 ([see this internal link](https://app.posthog.com/insights?insight=TRENDS&interval=day&display=ActionsLineGraph&events=%5B%7B%22id%22%3A%22insight%20loaded%22%2C%22name%22%3A%22insight%20loaded%22%2C%22type%22%3A%22events%22%2C%22order%22%3A0%2C%22math%22%3A%22dau%22%7D%5D&filter_test_accounts=true&actions=%5B%5D&new_entity=%5B%5D&breakdown=false&breakdown_type&properties=%5B%7B%22key%22%3A%22insight%22%2C%22value%22%3A%5B%22STICKINESS%22%5D%2C%22operator%22%3A%22exact%22%2C%22type%22%3A%22event%22%7D%5D&date_from=2021-08-30&date_to=2021-09-06#personModal=%7B%22action%22%3A%7B%22id%22%3A%22insight%20loaded%22%2C%22type%22%3A%22events%22%2C%22order%22%3A0%2C%22name%22%3A%22insight%20loaded%22%2C%22math%22%3A%22dau%22%2C%22math_property%22%3Anull%2C%22properties%22%3A%5B%5D%7D%2C%22label%22%3A%22insight%20loaded%22%2C%22date_from%22%3A%222021-09-03%22%2C%22date_to%22%3A%222021-09-03%22%2C%22filters%22%3A%7B%22insight%22%3A%22TRENDS%22%2C%22interval%22%3A%22day%22%2C%22display%22%3A%22ActionsLineGraph%22%2C%22events%22%3A%5B%7B%22id%22%3A%22insight%20loaded%22%2C%22name%22%3A%22insight%20loaded%22%2C%22type%22%3A%22events%22%2C%22order%22%3A0%2C%22math%22%3A%22dau%22%7D%5D%2C%22filter_test_accounts%22%3Atrue%2C%22actions%22%3A%5B%5D%2C%22new_entity%22%3A%5B%5D%2C%22breakdown%22%3Afalse%2C%22breakdown_type%22%3Anull%2C%22properties%22%3A%5B%7B%22key%22%3A%22insight%22%2C%22value%22%3A%5B%22STICKINESS%22%5D%2C%22operator%22%3A%22exact%22%2C%22type%22%3A%22event%22%7D%5D%2C%22date_from%22%3A%222021-08-30%22%2C%22date_to%22%3A%222021-09-06%22%7D%2C%22saveOriginal%22%3Atrue%7D))

The same thing happens with a [breakdown query](https://app.posthog.com/insights?insight=TRENDS&interval=day&display=ActionsLineGraph&events=%5B%7B%22id%22%3A%22insight%20loaded%22%2C%22name%22%3A%22insight%20loaded%22%2C%22type%22%3A%22events%22%2C%22order%22%3A0%2C%22math%22%3A%22dau%22%7D%5D&filter_test_accounts=true&properties=%5B%5D&actions=%5B%5D&new_entity=%5B%5D&breakdown=insight&breakdown_type=event)

## Expected behavior

The person modal should have 17 people

## How to reproduce

1. Go to link above
2. Click on sep 3
3. Verify there are 25 people

## Environment

- [ ] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: _please provide_

## Additional context

Looks like when passing through the date as 3rd of september, the query looks like this, which is probably where the 25 comes from (3rd + 4th of sept combined):
![image](https://user-images.githubusercontent.com/1727427/132249205-22c77f31-aee8-4d6a-819f-eafecd02ad46.png)


cc @EDsCODE @macobo 


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

posthog/api/test/test_action_people.py
event="sign up",
                        distinct_id=f"blabla_{i}",
                        properties={"$some_property": "value"},
                    )
            event_response = self.client.get(
                "/api/action/people/",
                data={
                    "date_from": "2020-01-01",
                    "date_to": "2020-01-31",
                    "interval": "day",
                    ENTITY_TYPE: "events",
                    ENTITY_ID: "sign up",
                    "display": "ActionsLineGraphCumulative",
                },
            ).json()
            self.assertEqual(event_response["results"][0]["count"], 80)
            with freeze_time("2020-01-31 00:06:34"):
                event_response = self.client.get(
                    "/api/action/people/",
                    data={
                        "date_from": "-30d",
                        "date_to": "2020-01-31",
                        "interval": "day",
                        ENTITY_TYPE: "events",
                        ENTITY_ID: "sign up",
                        "display": "ActionsLineGraphCumulative",
                    },
                ).json()
                self.assertEqual(event_response["results"][0]["count"], 80)
        def _create_breakdown_events(self):