Option to change pandas.Timestamp format when printing dataframe


#### Problem description
To use pandas.rolling, I had to convert my float64 nanoseconds timestamps to pandas.Timestamp. 
Timestamps now appear nicer on matplotlib plots but when debugging and plotting `df.head()`, i would like to see the timestamp in nanosecond format rather than `Timestamp.__repr()__` that prints the day/month/year (in my case the same for every row).

Every (stackoverflow) I could find recommand to create a new column with the right format. I would like to avoid that since I find it overkill.
As it's a temporary/printing issue, I think it falls into https://pandas.pydata.org/pandas-docs/stable/options.html#available-options and I would be happy with that.
What do you think ?

#### Expected Output

Version 0.23.4