utcnow() and utcfromtimestamp are semi-deprecated functions because they do not return tz-aware datetime objects and because in all functions that require a time zone offset (like `timestamp`), naive datetimes are treated as *local* times.

If you want to use tz-aware datetime objects (which will have the correct behavior), you should simply pass a time zone to the `tz` parameter of `now()` and `fromtimestamp`, respectively, so:

```
from datetime import datetime, timezone
a = datetime.now(tz=timezone.utc)
b = a.timestamp()
c = datetime.fromtimestamp(b, tz=timezone.utc)
assert a == c
```

I will note that because of the way aware datetime comparison semantics works, `a == c` will be true no matter what `tz` object you pass to `fromtimestamp`.

If I rewrite your example with equivalent commands that do not use `utcnow`, you will hopefully see how it works:

```
from datetime import datetime, timezone
from dateutil.tz import tzlocal

a = datetime.now(tz=timezone.utc).replace(tzinfo=None)
b = a.replace(tzinfo=tzlocal()).timestamp()
c = datetime.fromtimestamp(b, tz=timezone.utc).replace(tzinfo=None)
assert a == c
```

As you can see, in `a` you discard the time zone information associated with the datetime, and so in `b` it is implicitly taken to be "local time", shifting it by however many hours from UTC your local time is.

I will answer the hashability question in a separate e-mail, but I don't see how this has much to do with hashability.

P.S. Accidentally sent this to just Brock - Brock, sorry you are getting this twice.

On 4/15/19 8:01 PM, Brock Mendel wrote:
This has come up in pandas.Timestamp (which subclasses datetime).  The issue is internal consistency and round-trips.  Intuitively, we would expect:

```
a = datetime.utcnow()
b = a.timestamp()
c = datetime.utcfromtimestamp(b)
assert a == b
```

but this fails.  (Note: it works for `datetime.now()` with `datetime.fromtimestamp()`, though that is partially because of weird-to-me behavior of `timestamp()` for naive datetimes).

It would succeed if utcnow and utcfromtimestamp returned tz-aware datetime objects.  Thoughts?


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