Pandas using matplot displays an incorrect year on the x-axis date
#### Code

```python
# -*- coding: UTF-8 -*-

import pandas as pd
import datetime
import matplotlib.pyplot as plt
import matplotlib.dates as mdates

hoje = datetime.datetime.now()
data = hoje.strftime("%Y%m%d")
dados_url = 'https://covid.saude.gov.br/assets/files/COVID19_'+data+'.csv'

try:
    print(dados_url)
    dados = pd.read_csv(dados_url, sep=';', parse_dates=['data'],  dayfirst=True)
except Exception as e:
    print("Os dados para a data corrente ainda não foram atualizados, buscando dados do dia anterior...")
    print(e)
    DD = datetime.timedelta(days=1)
    hoje = hoje - DD
    data = hoje.strftime("%Y%m%d")
    print(str(hoje))
    dados_url = 'https://covid.saude.gov.br/assets/files/COVID19_'+data+'.csv'
    print(str(dados_url))
    dados = pd.read_csv(dados_url, sep=';', parse_dates=['data'],  dayfirst=True)

#pd.set_option('display.max_rows', None)

dados_alagoas = dados[dados['estado'] == 'AL']
dados_alagoas.set_index('data',inplace=True)
#print(dados_alagoas)

plt.style.use('ggplot')

fig, ax = plt.subplots(figsize=(30,15))
dados_alagoas.plot(ax=ax, rot=75)

#grafico em barras
#dados_alagoas.plot(ax=ax, rot=75, kind='bar', width=2.0)

ax.xaxis.set_major_locator(mdates.DayLocator(interval=1))
ax.xaxis.set_major_formatter(mdates.DateFormatter('%d/%m/%y'))
ax.set_title('Incidência do COVID-19 em Alagoas em '+hoje.strftime('%d/%m/%Y'))
ax.set_ylabel('Ocorrências')
ax.set_xlabel('Data')
plt.show()

```
#### Problem description
In the graph, the date axis is not being displayed correctly with date formatting, the year that should be "2020" and is displayed as "51"

#### Output of ``pd.show_versions()``
INSTALLED VERSIONS
------------------
commit           : None
python           : 3.8.2.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.4.28-1-MANJARO
machine          : x86_64
processor        : 
byteorder        : little
LC_ALL           : None
LANG             : pt_BR.UTF-8
LOCALE           : pt_BR.UTF-8

pandas           : 1.0.3
numpy            : 1.18.2
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 46.1.3
Cython           : 0.29.16
pytest           : 5.4.1
hypothesis       : None
sphinx           : 2.4.4
blosc            : 1.8.3
feather          : None
xlsxwriter       : 1.2.8
lxml.etree       : 4.5.0
html5lib         : 1.0.1
pymysql          : 0.9.3
psycopg2         : 2.8.4 (dt dec pq3 ext lo64)
jinja2           : 2.11.1
IPython          : 7.13.0
pandas_datareader: 0.8.1
bs4              : 4.8.2
bottleneck       : 1.3.2
fastparquet      : None
gcsfs            : None
lxml.etree       : 4.5.0
matplotlib       : 3.2.1
numexpr          : 2.7.1
odfpy            : None
openpyxl         : 3.0.3
pandas_gbq       : None
pyarrow          : None
pytables         : None
pytest           : 5.4.1
pyxlsb           : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : 1.3.15
tables           : 3.6.1
tabulate         : 0.8.7
xarray           : None
xlrd             : 1.2.0
xlwt             : 1.3.0
xlsxwriter       : 1.2.8
numba            : None
None





![Figure_1](https://user-images.githubusercontent.com/8952225/78317749-81d49600-7539-11ea-9de4-c2c62107c2f0.png)



