Q:

Is there any other ways to sort dataframe column values by Date (Year-Month) on

Initially it was in year-month order but when sum by month operation performed, the output were by-default sorted in ascending order.
Operation performed: sales=sales.groupby([(sales['Date'])]).sum()
print(sales)
Output:
        Quantity
Date              
2010-Dec      3130
2011-Jan      5230
2011-Feb      1710
2011-Mar      1904  

Expected output:
        Quantity
Date              
2010-Dec      3130
2011-Jan      5230
2011-Feb      1710
2011-Mar      1904

Tried:  sales=sales.sort_values(by=sales.index, ascending=False) but didn't work.
Tried to reset index by: sales=(sales.groupby([(sales['Date'])]).sum()).reset_index(False) and
sort but didn't work

A:

Yes we can do it convert to datetime them we do argsort 
df=df.iloc[pd.to_datetime(df.index).argsort()]
df
          Quantity
Date              
2010-Dec      3130
2011-Jan      5230
2011-Feb      1710
2011-Mar      1904

