Imagine I have the following pivot_table from pandas:


```
		births
1	1	4009.225
	2	4247.400
	3	4500.900
	4	4571.350
	5	4603.625
```

It was created using 
`birth2_by_date=birth2.pivot_table("births",[birth2.index.month,birth2.index.day])` 
where `birth2.index` came from a [pandas.to_datetime function](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.to_datetime.html).

I want to name the indices of this pivot_table `Month` and `Day`.

To that effect, I've tried `birth2_by_date.index.name=("month","day")` without success...