I have the following code:

commit_date = get_last_commit_date() # returns datetime obj: 2022-08-25 13:32:12
pr_date = datetime.fromisoformat(ISO_CODE) # returns 2022-08-24 19:15:07

Notice how commit_date is Aug. 25 and pr_date is Aug. 24. I want to find the difference in days which should be 1 day.

Now doing print((pr_date - commit_date).days) will give -1 days. So naturally I swap them and do print((commit_date - pr_date).days) but it reports 0 days? How can it be 0 days? Why isn't it reporting 1 day time difference?

CodePudding user response：

This is a rounding error; since the dates are not at the exact same time, the difference between the two days can end up being on a different day depending on the order you subtract them.

i.e

2022-08-24 19:15:07 - 2022-08-25 13:32:12 = {0}-{0}-{-1} {5}:{42}{55}

and

2022-08-25 13:32:12 - 2022-08-24 19:15:07 = {0}-{0}-{0} {18}:{17}{05}

The difference of hours between 13-19 means the hour is -6. Negative hours in a day means it is a day before, so the difference is 0 days and 18 hours instead of 1 for the second calculation.

If you're trying to find the difference in days as opposed to total difference in date time, you wanna subtract the "day" attributes of the individual datetimes as opposed to the entire date time.

If you do

print((pr_date.day - commit_date.day))
>> -1
print((commit_date.day - pr_date.day))
>> 1

You get the right difference between days. If you use absolute value i.e

print(abs(pr_date.day - commit_date.day))
>> 1

The order of the days doesn't matter, and you can find the difference like that.