Datetime series slicing - error without loc()
Problem:
Date time series on slicing might produce errors for different reasons(change in data format for each, unsorted DateTime inputs etc.)  which can be avoided with "loc() on the DateTime".
The error was like *** Slicing with this method is *always* positional.***

After correcting the Issue : (Screenshots)
https://docs.google.com/document/d/1L5Ei0q5BfHCTnfzG43exvTug_N1OE7UEmxbgB0KjIh4/edit?usp=sharing

Issue: 43223

Code testing :
    
    import pandas as pd
    import numpy as np
    df = pd.DataFrame(
        {'ind': [i for i in range(5)]}, 
        index=pd.DatetimeIndex(["11.01.2011 22:00", "11.01.2011 23:00", "12.01.2011 00:00", "2011-01-13 00:00","2011-01-14 00:00"]))
    
    df.loc["2011-01-01": "2011-11-01"].plot()

Test Dataset:

                     ind
        2011-11-01 22:00:00    0
        2011-11-01 23:00:00    1
        2011-12-01 00:00:00    2
        2011-01-13 00:00:00    3
        2011-01-14 00:00:00    4

The above code works perfectly with loc() added and is one of the test case examples.

- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry
