date_range produces wrong values when overflowing

[jorisvandenbossche]

In the following case, you now get a RuntimeWarning. But shouldn't we rather error on this?

In [23]: pd.date_range('1/1/2000', periods=100000, freq='D')
/home/joris/scipy/pandas/pandas/tseries/index.py:1944: RuntimeWarning: overflow encountered in long_scalars
  e = b + np.int64(periods) * stride
/home/joris/scipy/pandas/pandas/tseries/index.py:1954: RuntimeWarning: overflow encountered in long_scalars
  data = np.arange(b, e, stride, dtype=np.int64)
Out[23]: 
DatetimeIndex([          '2000-01-01 00:00:00',
                         '2000-01-02 00:00:00',
                         '2000-01-03 00:00:00',
                         '2000-01-04 00:00:00',
                         '2000-01-05 00:00:00',
                         '2000-01-06 00:00:00',
                         '2000-01-07 00:00:00',
                         '2000-01-08 00:00:00',
                         '2000-01-09 00:00:00',
                         '2000-01-10 00:00:00',
               ...
               '1689-03-17 00:25:26.290448384',
               '1689-03-18 00:25:26.290448384',
               '1689-03-19 00:25:26.290448384',
               '1689-03-20 00:25:26.290448384',
               '1689-03-21 00:25:26.290448384',
               '1689-03-22 00:25:26.290448384',
               '1689-03-23 00:25:26.290448384',
               '1689-03-24 00:25:26.290448384',
               '1689-03-25 00:25:26.290448384',
               '1689-03-26 00:25:26.290448384'],
              dtype='datetime64[ns]', length=100000, freq='D')

In [24]: pd.__version__
Out[24]: '0.19.0rc1+2.gd8cd33b'

In [25]: np.__version__
Out[25]: '1.11.1'

[jreback]

might be now showing because of the np.errstate changes. yes an overflow is not good here (in general we can/should catch the overflow in an offset and just return a datetime, rather than a Timestamp) But here I think its an error as we can't represent that range.

[jreback]

something like this would work I think

try:
    with np.errstate(over='raise'):
         e = b + .....
except FloatingPointError:
    raise ValueError("cannot create a date range like that")