DateFormatter('%Y') for x-axis labels gives strange output for a specific date value
```python
import numpy as np
import pandas as pd
import matplotlib.dates as md
import matplotlib.pyplot as plt

data = {
    'date': [pd.Timestamp(2014, 9, 28), pd.Timestamp(2014, 10, 5), pd.Timestamp(2014, 10, 12)],
    'val': [0.37,0.44,0.44]
}
df = pd.DataFrame(data=data)
ax = df.plot(x='date', y='val')
ax.xaxis.set_major_formatter(md.DateFormatter('%Y'))
```
#### Problem description
When I run the above code the plot generated should have x axis tick labels showing the year e.g. **'2014', '2014', '2014'**, etc.  Instead it has the labels **'0007', '0007', '0007'**.

If I increment the last date from '**2014-10-12**' to '**2014-10-13**' in the 'data' variable by one day (or really change it to anything else) like this:

```python
data = {
    'date': [pd.Timestamp(2014, 9, 28), pd.Timestamp(2014, 10, 5), pd.Timestamp(2014, 10, 13)],
    'val': [0.37,0.44,0.44]
}
```
Then rerun it, it works as expected.

#### Expected Output
x label on generated plot figure should be **'2014', '2014', '2014', ...**

#### What else have you tried?
I ran the same data using only numpy and matplotlib to rule that out as a source of the unexpected output and I was given the expected x-axis label formatting with **'2014', '2014', '2014'**, etc.  Here is my code for that;

```python
data = np.array([
    (np.datetime64('2014-09-28'), 0.37),
    (np.datetime64('2014-10-05'), 0.44),
    (np.datetime64('2014-10-12'), 0.44)], 
    dtype=[('date', 'datetime64[D]'), ('val', float)
])

data = data.view(np.recarray)
fig, ax = plt.subplots()
ax.plot(data.date, data.val)
ax.xaxis.set_major_formatter(md.DateFormatter('%Y'))
plt.show()
```
#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.8.final.0
python-bits: 64
OS: Darwin
OS-release: 18.5.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_AU.UTF-8
LOCALE: en_AU.UTF-8

pandas: 0.24.2
pytest: None
pip: 19.0.3
setuptools: 41.0.0
Cython: None
numpy: 1.16.2
scipy: 1.2.1
pyarrow: None
xarray: 0.11.3
IPython: 7.4.0
sphinx: None
patsy: None
dateutil: 2.8.0
pytz: 2019.1
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 3.0.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml.etree: 4.3.3
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10.1
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None
</details>
