DatetimeIndex.values yields unexpected results
```
import pandas as pd

dates = pd.date_range('1997-12-31', periods=5)
print('Iterating through DatetimeIndex:')
for date in dates:
    print(date)
print('Iterating through DatetimeIndex.values:')
for date in dates.values:
    print(date)
```

> Iterating through DatetimeIndex:
> 1997-12-31 00:00:00
> 1998-01-01 00:00:00
> 1998-01-02 00:00:00
> 1998-01-03 00:00:00
> 1998-01-04 00:00:00
> Iterating through DatetimeIndex.values:
> 1970-01-11 48:00:00
> 1970-01-11 72:00:00
> 1970-01-11 96:00:00
> 1970-01-11 120:00:00
> 1970-01-11 144:00:00

Is this the way it should be?
