Try:
>>> from datetime import datetime, timedelta
>>> now = datetime.now()
>>> now - (now + timedelta(days=1))
datetime.timedelta(-1)That a timedelta can be represented in multiple ways is alone quite surprising but some of the representations that happen can be very confusing. I think the example I gave which represents "-1 day and a few microseconds" as "-2 days + 86399 milliseconds + 999969 microseconds" is very surprising and it commonly happens in practice.
For comparison, here's what postgres does:
postgres=> select now() - (now() + '12 milliseconds'::interval + '1 day'::interval);
?column?
-----------------------
-1 days -00:00:00.012
(1 row) d1 = datetime(2012, 1, 1, 1, 2, 3, tzinfo=pytz.UTC)
d2 = datetime(2011, 12, 31, 22, 2, 3, tzinfo=pytz.UTC)
delta = d2 - d1
delta.days
-1
delta.seconds
75600
d1 = Pendulum(2012, 1, 1, 1, 2, 3)
d2 = Pendulum(2011, 12, 31, 22, 2, 3)
delta = d2 - d1
delta.days
0
delta.hours
-3