read_csv interprets index column as dates
I loaded a dataset with an index column going from 1 to 304. Then I try to get the repr of the dataframe, but it raises `ValueError: year=100 is before 1900; the datetime strftime() methods require year >= 1900`. Looking at `df.index` shows that the numeric indices have been transformed into datetimes (the first 31 to days of this month, 32-60 as years 20xx, 61-99 as years 19xx, and higher numbers as a raw year).
