1. Dates beyond year 9999 aren't a prerequisite for infinite types - I see that as a separate issue. The fact that we can't represent dates between 9999 and infinity doesn't make infinity less useful :)

2 & 3. Yeah, string representation is something that needs to be decided on - that's a big potential bikeshed. My preference at this stage would be for these to be called e.g. date.inf_future and date.inf_past, and the string representation to be the same. timedelta could simply have timedelta.infinity, and since it supports __neg__, -timedelta.infinity would work just fine. I'd like to hear other views though.

4. In my implementation, `datetime.now() - DATETIME_NEG_INF == TIMEDELTA_POS_INF`. I haven't implemented the division dunder methods yet, but by analogy to float, I would say that `TIMEDELTA_POS_INF / timedelta(days=1) == float("inf")` and `TIMEDELTA_POS_INF // timedelta(days=1)` raises TypeError (the latter returns nan in the case of float).

Thanks,

Alex

On Wed, Jun 17, 2020 at 2:57 PM Serhiy Storchaka <storchaka@gmail.com> wrote:

16.06.20 13:54, Alexander Hill пише:
> I’d like to propose support for infinite dates, datetimes and
> timedeltas. They're very useful when you need to model ranges with one
> or both ends unbounded (e.g. “forever starting from June 15th 2020”).
>
> Without first-class infinite values, you can use None, or you can use
> the `min` and `max` attributes of Python’s datetime types, or some other
> arbitrary large values. Using None means you need to implement a path
> for None, and a path for everything else, and your various infinite
> values are indistinguishable. Using max/min means comparisons just work,
> but calculations need special treatment and you’re fundamentally
> misrepresenting your meaning.
>
> Temporal infinities give the best of both worlds: infinite values that
> interoperate seamlessly with the built-in types and behave sensibly and
> predictably. They’re also supported by Postgres!

First we need to solve some problems.

1. Parsing dates with more than 4-digit year. Note that many external
implementations do not support such data, so we need a way to restrict
the data range when convert them to string representation.

2. String representations and parsing for negative data.

3. String representations and parsing for infinity data (positive and
negative).

4. If datetime.min will be the negative infinity, then what will be the
result of `datetime.now() - datetime.min`? Or `(datetime.now() -
datetime.min) // timedelta(days=1)`?
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