## Bug description

There seems to be an issue with `get_available_timezones_with_offsets`, not sure at what point it broke.

```
Traceback (most recent call last):
    response = view_func(request, *args, **kwargs)
  File "/posthog/posthog/views.py", line 184, in preflight_check
    "available_timezones": get_available_timezones_with_offsets(),
    raise NonExistentTimeError(dt)
```

## Expected behavior
Preflight should work and the timezone list be returned correctly.


## How to reproduce

1. Just check `/_preflight` request

## Environment

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

## Additional context

Tagging @Twixes as you have more context on this.

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

posthog/utils.py
import lzstring
import pytz
from dateutil import parser
from dateutil.relativedelta import relativedelta
from django.conf import settings
from django.core.cache import cache
from django.db.models.query import QuerySet
from django.db.utils import DatabaseError
from django.http import HttpRequest, HttpResponse
from django.template.loader import get_template
from django.utils import timezone
from rest_framework.exceptions import APIException
from sentry_sdk import capture_exception, push_scope
from posthog.redis import get_client
from posthog.settings import print_warning
DATERANGE_MAP = {
    "minute": datetime.timedelta(minutes=1),
    "hour": datetime.timedelta(hours=1),
    "day": datetime.timedelta(days=1),
    "week": datetime.timedelta(weeks=1),
    "month": datetime.timedelta(days=31),
}
ANONYMOUS_REGEX = r"^([a-z0-9]+\-){4}([a-z0-9]+)$"
__location__ = os.path.realpath(os.path.join(os.getcwd(), os.path.dirname(__file__)))
def format_label_date(date: datetime.datetime, interval: str) -> str:
    labels_format = "%a. {day} %B"
    if interval == "hour" or interval == "minute":
        labels_format += ", %H:%M"
    return date.strftime(labels_format.format(day=date.day))
def absolute_uri(url: Optional[str] = None) -> str: