Matplotlib.plot_date automatically adds in dates no on my data series, why and how to avoid?

I'm new to python/matplotlib, while I'm experimenting I encourage this strange behavior that the produced chart always shows those points(dates) that ain't exist on my series. I tried to search from the doc and web but couldn't find much clue. Here's how I produced the chart:

import pymysql  import datetime  import pandas as pd  import matplotlib.pyplot as plt    serial_no = '163406'  start_date = '2020-06-28'    mysql = pymysql.connect(host="localhost",port=3306,user="dbuser",passwd="psword",db="expdb")  cursor = mysql.cursor()    sql = "select r.t_date ,r.acc_av from expdb.records r \          where r.sn = '"+serial_no+"'and r.t_date >= '"+start_date+"' order by r.t_date ASC"    data= pd.read_sql(sql, mysql, parse_dates=['t_date'])  data = data.set_index('t_date')    plt.plot_date(fdata.index,data[['acc_av']],linestyle=':', marker='.', label='acc av')    plt.show()  

The datatype of datatype:

fund_df.info()    <class 'pandas.core.frame.DataFrame'>  DatetimeIndex: 32 entries, 2020-11-30 to 2021-01-13  Data columns (total 1 columns):   #   Column  Non-Null Count  Dtype    ---  ------  --------------  -----     0   acc_av  32 non-null     float64  dtypes: float64(5)  memory usage: 1.5 KB  

A few sample data:

data.head(10)              acc_av  t_date    2020-11-30  7.0706  2020-12-01  7.2280  2020-12-02  7.2234  2020-12-03  7.2360  2020-12-04  7.2889  2020-12-07  7.2660  2020-12-08  7.2721  2020-12-09  7.1850  2020-12-10  7.1953  2020-12-11  7.1542  

There are few days certainly not in the series, ie 2020-12-05, 2020-12-06.

From the chart it produced, even the markers of these nonexistent dates, the timeframe appears still exists on the chart, that showing longer interval space from 12-04 to 12-07, for instance, it's the same regardless I used plt.plot() or plt.plot_date(). Is there a way to avoid matplotlib automatically put in these nonexistent date back into the chart ?

The produced chart

https://stackoverflow.com/questions/65820966/matplotlib-plot-date-automatically-adds-in-dates-no-on-my-data-series-why-and-h January 21, 2021 at 11:56AM