<p dir="auto">Just saw this, haven't looked yet</p>
<table role="table">
<thead>
<tr>
<th>test</th>
<th>pass</th>
<th>skip</th>
<th>xfail</th>
</tr>
</thead>
<tbody>
<tr>
<td>Interval</td>
<td>551</td>
<td>640</td>
<td>0</td>
</tr>
<tr>
<td>Period</td>
<td>472</td>
<td>0</td>
<td>1</td>
</tr>
<tr>
<td>Both</td>
<td>789</td>
<td>829</td>
<td>1</td>
</tr>
</tbody>
</table>
<p dir="auto">commands:</p>
<ul dir="auto">
<li><code class="notranslate">pytest pandas/tests/indexes/period/</code></li>
<li><code class="notranslate">pytest pandas/tests/indexes/period/</code></li>
<li><code class="notranslate">pytest pandas/tests/indexes/interval/ pandas/tests/indexes/period/</code></li>
</ul>
<p dir="auto">Incorrect <code class="notranslate">dt.weekofyear</code> calculation? I was expecting <code class="notranslate">weekofyear</code>/<code class="notranslate">week</code> for <code class="notranslate">20050101</code> would  be <code class="notranslate">0</code></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="In [1442]: df
Out[1442]:
   A         B
0  1  20050121
1  2  20050111
2  3  20050205
3  4  20050101

In [1443]: pd.to_datetime(df.B, format='%Y%m%d').dt.week
Out[1443]:
0     3
1     2
2     5
3    53
Name: B, dtype: int64

In [1444]: pd.to_datetime(df.B, format='%Y%m%d').dt.weekofyear
Out[1444]:
0     3
1     2
2     5
3    53
Name: B, dtype: int64

In [1445]: pd.to_datetime(df.B, format='%Y%m%d').dt.strftime('%W')
Out[1445]:
0    03
1    02
2    05
3    00
Name: B, dtype: object"><pre class="notranslate"><span class="pl-v">In</span> [<span class="pl-c1">1442</span>]: <span class="pl-s1">df</span>
<span class="pl-v">Out</span>[<span class="pl-c1">1442</span>]:
   <span class="pl-v">A</span>         <span class="pl-v">B</span>
<span class="pl-c1">0</span>  <span class="pl-c1">1</span>  <span class="pl-c1">20050121</span>
<span class="pl-c1">1</span>  <span class="pl-c1">2</span>  <span class="pl-c1">20050111</span>
<span class="pl-c1">2</span>  <span class="pl-c1">3</span>  <span class="pl-c1">20050205</span>
<span class="pl-c1">3</span>  <span class="pl-c1">4</span>  <span class="pl-c1">20050101</span>

<span class="pl-v">In</span> [<span class="pl-c1">1443</span>]: <span class="pl-s1">pd</span>.<span class="pl-en">to_datetime</span>(<span class="pl-s1">df</span>.<span class="pl-v">B</span>, <span class="pl-s1">format</span><span class="pl-c1">=</span><span class="pl-s">'%Y%m%d'</span>).<span class="pl-s1">dt</span>.<span class="pl-s1">week</span>
<span class="pl-v">Out</span>[<span class="pl-c1">1443</span>]:
<span class="pl-c1">0</span>     <span class="pl-c1">3</span>
<span class="pl-c1">1</span>     <span class="pl-c1">2</span>
<span class="pl-c1">2</span>     <span class="pl-c1">5</span>
<span class="pl-c1">3</span>    <span class="pl-c1">53</span>
<span class="pl-v">Name</span>: <span class="pl-v">B</span>, <span class="pl-s1">dtype</span>: <span class="pl-s1">int64</span>

<span class="pl-v">In</span> [<span class="pl-c1">1444</span>]: <span class="pl-s1">pd</span>.<span class="pl-en">to_datetime</span>(<span class="pl-s1">df</span>.<span class="pl-v">B</span>, <span class="pl-s1">format</span><span class="pl-c1">=</span><span class="pl-s">'%Y%m%d'</span>).<span class="pl-s1">dt</span>.<span class="pl-s1">weekofyear</span>
<span class="pl-v">Out</span>[<span class="pl-c1">1444</span>]:
<span class="pl-c1">0</span>     <span class="pl-c1">3</span>
<span class="pl-c1">1</span>     <span class="pl-c1">2</span>
<span class="pl-c1">2</span>     <span class="pl-c1">5</span>
<span class="pl-c1">3</span>    <span class="pl-c1">53</span>
<span class="pl-v">Name</span>: <span class="pl-v">B</span>, <span class="pl-s1">dtype</span>: <span class="pl-s1">int64</span>

<span class="pl-v">In</span> [<span class="pl-c1">1445</span>]: <span class="pl-s1">pd</span>.<span class="pl-en">to_datetime</span>(<span class="pl-s1">df</span>.<span class="pl-v">B</span>, <span class="pl-s1">format</span><span class="pl-c1">=</span><span class="pl-s">'%Y%m%d'</span>).<span class="pl-s1">dt</span>.<span class="pl-en">strftime</span>(<span class="pl-s">'%W'</span>)
<span class="pl-v">Out</span>[<span class="pl-c1">1445</span>]:
<span class="pl-c1">0</span>    <span class="pl-c1">03</span>
<span class="pl-c1">1</span>    <span class="pl-c1">02</span>
<span class="pl-c1">2</span>    <span class="pl-c1">05</span>
<span class="pl-c1">3</span>    <span class="pl-c1">00</span>
<span class="pl-v">Name</span>: <span class="pl-v">B</span>, <span class="pl-s1">dtype</span>: <span class="pl-s1">object</span></pre></div>
<h4 dir="auto">Output of <code class="notranslate">pd.show_versions()</code></h4>
<details>
<h2 dir="auto">INSTALLED VERSIONS</h2>
<p dir="auto">commit: None<br>
python: 2.7.12.final.0<br>
python-bits: 64<br>
OS: Windows<br>
OS-release: 7<br>
machine: AMD64<br>
processor: Intel64 Family 6 Model 61 Stepping 4, GenuineIntel<br>
byteorder: little<br>
LC_ALL: None<br>
LANG: None<br>
LOCALE: None.None</p>
<p dir="auto">pandas: 0.21.0.dev+397.g234b042<br>
pytest: 3.2.0<br>
pip: 9.0.1<br>
setuptools: 36.2.7<br>
Cython: 0.24.1<br>
numpy: 1.12.1<br>
scipy: 0.19.1<br>
pyarrow: None<br>
xarray: None<br>
IPython: 5.1.0<br>
sphinx: 1.4.6<br>
patsy: 0.4.1<br>
dateutil: 2.5.3<br>
pytz: 2017.2<br>
blosc: None<br>
bottleneck: 1.2.0<br>
tables: 3.2.2<br>
numexpr: 2.6.2<br>
feather: None<br>
matplotlib: 2.0.2<br>
openpyxl: 2.3.2<br>
xlrd: 1.0.0<br>
xlwt: 1.1.2<br>
xlsxwriter: 0.9.3<br>
lxml: 3.6.4<br>
bs4: 4.5.1<br>
html5lib: 0.999999999<br>
sqlalchemy: 1.0.13<br>
pymysql: 0.7.9.None<br>
psycopg2: None<br>
jinja2: 2.8<br>
s3fs: None<br>
fastparquet: None<br>
pandas_gbq: None<br>
pandas_datareader: None</p>
</details>