## Is your feature request related to a problem?

#4947 added a new query to the backend – time to convert. It works well, just one point is kind of rough: bin width and count.

## Describe the solution you'd like

Currently the number of bins is hardcoded. Ideally we should have two options:
- return a user-specified number of bins,
- otherwise infer a reasonable number of bins using some algorithm (auto option).

@alexkim205 [suggested](https://github.com/PostHog/posthog/issues/4855#issuecomment-872423877) the [Freedman-Diaconis rule](https://en.wikipedia.org/wiki/Freedman%E2%80%93Diaconis_rule) for determining bin width (and interval based on that), but unfortunately from my testing its formula would not be the most practical – it's great for keeping a pretty constant "smoothness" of the histogram esp. with normal distribution, but we face some additional constraints that make it less than ideal:
- we can't have histograms too dense visually in the UI, from my testing a practical limit is 60 bins (above that it gets too dense),
- our data generally doesn't follow much of a normal distribution.

Clamping may help though, or maybe a different formula may work better outright – I'll be testing this.

## Additional context

Issue pertaining to the experience of time to convert: #4855

#### *Thank you* for your feature request – we love each and every one!

posthog/models/filters/mixins/common.py
result_dict = {}
        if self._date_from:
            result_dict.update(
                {
                    "date_from": self._date_from.isoformat()
                    if isinstance(self._date_from, datetime.datetime)
                    else self._date_from
                }
            )
        if self._date_to:
            result_dict.update(
                {
                    "date_to": self._date_to.isoformat()
                    if isinstance(self._date_to, datetime.datetime)
                    else self._date_to
                }
            )
        return result_dict
class EntitiesMixin(BaseParamMixin):
    @cached_property
    def entities(self) -> List[Entity]:
        _entities: List[Entity] = []
        if self._data.get(ACTIONS):
            actions = self._data.get(ACTIONS, [])
            if isinstance(actions, str):
                actions = json.loads(actions)
            _entities.extend([Entity({**entity, "type": TREND_FILTER_TYPE_ACTIONS}) for entity in actions])
        if self._data.get(EVENTS):
            events = self._data.get(EVENTS, [])
            if isinstance(events, str):