[Numpy-discussion] datetime64 1970 issue

Charles R Harris charlesr.harris@gmail....
Tue Apr 16 23:32:08 CDT 2013


On Tue, Apr 16, 2013 at 6:45 PM, Benjamin Root <ben.root@ou.edu> wrote:

>
> On Tue, Apr 16, 2013 at 7:45 PM, Ondřej Čertík <ondrej.certik@gmail.com>wrote:
>
>> On Tue, Apr 16, 2013 at 4:55 PM, Bob Nnamtrop <bob.nnamtrop@gmail.com>
>> wrote:
>> > I am curious if others have noticed an issue with datetime64 at the
>> > beginning of 1970. First:
>> >
>> > In [144]: (np.datetime64('1970-01-01') - np.datetime64('1969-12-31'))
>> > Out[144]: numpy.timedelta64(1,'D')
>> >
>> > OK this look fine, they are one day apart. But look at this:
>> >
>> > In [145]: (np.datetime64('1970-01-01 00') - np.datetime64('1969-12-31
>> 00'))
>> > Out[145]: numpy.timedelta64(31,'h')
>> >
>> > Hmmm, seems like there are 7 extra hours? Am I missing something? I
>> don't
>> > see this at any other year. This discontinuity makes it hard to use the
>> > datetime64 object without special adjustment in ones code. I assume
>> this a
>> > bug?
>>
>> Indeed, this looks like a bug, I can reproduce it on linux as well:
>>
>> In [1]: import numpy as np
>>
>> In [2]: np.datetime64('1970-01-01') - np.datetime64('1969-12-31')
>> Out[2]: numpy.timedelta64(1,'D')
>>
>> In [3]: np.datetime64('1970-01-01 00') - np.datetime64('1969-12-31 00')
>> Out[3]: numpy.timedelta64(31,'h')
>>
>>
> Maybe, maybe not... were you alive then?  For all we know, Charles and co.
> were partying an extra 7 hours every day back then?
>
>
Dude, it was the 60's, no one remembers.

Chuck
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