Python - time difference in milliseconds not working for me

The correct answer (in 2020) is:

>>> from datetime import timedelta
>>> timedelta(days=1, milliseconds=50) / timedelta(milliseconds=1)
86400050.0

The other answers lose precision and/or are more verbose.

Try using total_seconds method:

print time_diff_wind.total_seconds() * 1000

That method is equivalent to: (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6) / 10**6

Note: It's available since version 2.7

I faced this issue as well, but in my case I need real milliseconds precision, so using total_seconds() * 1000 isn't an option for me, so what I did is:

def millis_interval(start, end):
    """start and end are datetime instances"""
    diff = end - start
    millis = diff.days * 24 * 60 * 60 * 1000
    millis += diff.seconds * 1000
    millis += diff.microseconds / 1000
    return millis

I hope this helps someone else! :)

>>> a = datetime.datetime.now()
>>> b = datetime.datetime.now()
>>> a
datetime.datetime(2013, 8, 25, 2, 5, 1, 879000)
>>> b
datetime.datetime(2013, 8, 25, 2, 5, 8, 984000)
>>> a - b
datetime.timedelta(-1, 86392, 895000)
>>> b - a
datetime.timedelta(0, 7, 105000)
>>> (b - a).microseconds
105000
>>> (b - a).seconds
7
>>> (b - a).microseconds / 1000
105

your microseconds don't include the seconds that have passed