<p dir="auto">On x86:<br>
<code class="notranslate">&gt;&gt;&gt;np.float64(np.nan).astype('M8[ns]')</code><br>
<code class="notranslate">numpy.datetime64('NaT')</code></p>
<p dir="auto">On ARM:<br>
<code class="notranslate">&gt;&gt;&gt;np.float64(np.nan).astype('M8[ns]')</code><br>
<code class="notranslate">numpy.datetime64('1970-01-01T00:00:00.00000000')</code></p>
<p dir="auto">Some tests for pandas fail on ARM due to this difference</p>
<p dir="auto">Traceback (most recent call last):<br>
File "/root/venv/lib/python2.7/site-packages/pandas/tseries/tests/test_timeseries.py", line 4072, in test_NaT_cast<br>
assert_series_equal(result, expected)<br>
File "/root/venv/lib/python2.7/site-packages/pandas/util/testing.py", line 1049, in assert_series_equal<br>
check_less_precise, obj='{0}'.format(obj))<br>
File "pandas/src/testing.pyx", line 58, in pandas._testing.assert_almost_equal (pandas/src/testing.c:3887)<br>
File "pandas/src/testing.pyx", line 147, in pandas._testing.assert_almost_equal (pandas/src/testing.c:2769)<br>
File "/root/venv/lib/python2.7/site-packages/pandas/util/testing.py", line 915, in raise_assert_detail<br>
raise AssertionError(msg)<br>
AssertionError: Series are different</p>
<p dir="auto">Series values are different (100.0 %)</p>
<p dir="auto">originally detected while building fresh pandas for debian [1], and then verified with current master of numpy:</p>
<div class="highlight highlight-source-shell notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="(sid_powerpc-dchroot)yoh@partch:~/numpy$ python -c 'import numpy as np; print(np.array([np.nan]).astype(&quot;M8[ns]&quot;)); print np.__version__'; git describe --tags

['2262-04-10T00:12:45.292707840']
1.13.0.dev0+a4dca24
pre-removal-numpybook-3581-ga4dca24"><pre class="notranslate">(sid_powerpc-dchroot)yoh@partch:<span class="pl-k">~</span>/numpy$ python -c <span class="pl-s"><span class="pl-pds">'</span>import numpy as np; print(np.array([np.nan]).astype("M8[ns]")); print np.__version__<span class="pl-pds">'</span></span><span class="pl-k">;</span> git describe --tags

[<span class="pl-s"><span class="pl-pds">'</span>2262-04-10T00:12:45.292707840<span class="pl-pds">'</span></span>]
1.13.0.dev0+a4dca24
pre-removal-numpybook-3581-ga4dca24</pre></div>
<p dir="auto">expected result (e.g. on amd64 box):</p>
<div class="highlight highlight-source-shell notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="$&gt; python -c 'import numpy as np; print(np.array([np.nan]).astype(&quot;M8[ns]&quot;)); print np.__version__'; 
['NaT']
1.11.2"><pre class="notranslate">$<span class="pl-k">&gt;</span> python -c <span class="pl-s"><span class="pl-pds">'</span>import numpy as np; print(np.array([np.nan]).astype("M8[ns]")); print np.__version__<span class="pl-pds">'</span></span><span class="pl-k">;</span> 
[<span class="pl-s"><span class="pl-pds">'</span>NaT<span class="pl-pds">'</span></span>]
1.11.2</pre></div>
<p dir="auto">[1] <a href="https://buildd.debian.org/status/fetch.php?pkg=pandas&amp;arch=powerpc&amp;ver=0.19.1-2&amp;stamp=1480352140" rel="nofollow">https://buildd.debian.org/status/fetch.php?pkg=pandas&amp;arch=powerpc&amp;ver=0.19.1-2&amp;stamp=1480352140</a></p>
<p dir="auto">edit 1:  issue is not new (debian jessie/stable):</p>
<div class="highlight highlight-source-shell notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="(jessie_powerpc-dchroot)yoh@partch:~$ python -c 'import numpy as np; print(np.array([np.nan]).astype(&quot;M8[ns]&quot;)); print np.__version__'
['2262-04-10T00:12:45.292707840+0000']
1.8.2"><pre class="notranslate">(jessie_powerpc-dchroot)yoh@partch:<span class="pl-k">~</span>$ python -c <span class="pl-s"><span class="pl-pds">'</span>import numpy as np; print(np.array([np.nan]).astype("M8[ns]")); print np.__version__<span class="pl-pds">'</span></span>
[<span class="pl-s"><span class="pl-pds">'</span>2262-04-10T00:12:45.292707840+0000<span class="pl-pds">'</span></span>]
1.8.2</pre></div>