ENH: Timestamp/DTI. to epoch time

[jreback]

add a .to_epoch(unit='s') method to Timestamp and DatetimeIndex that returns the epoch for that unit. I think would default this to s as that seems pretty common, but allow any of our units.

In [19]: s = Series(pd.date_range('20160101',periods=3))

In [20]: s
Out[20]: 
0   2016-01-01
1   2016-01-02
2   2016-01-03
dtype: datetime64[ns]

In [21]: ((s-Timestamp(0)) / Timedelta('1s')).astype('i8')
Out[21]: 
0    1451606400
1    1451692800
2    1451779200
dtype: int64

[jreback]

xref #11022, #6741

[jreback]

This also works, but exposing internal impl, verbose and not user friendly

In [36]: Series(s.values.astype('datetime64[s]').astype('i8'), index=s.index)
Out[36]: 
0    1451606400
1    1451692800
2    1451779200
dtype: int64

[jorisvandenbossche]

If we would add user facing functionality, I think I would like to_epoch() most (certainly not something like int64[s] IMO)

[jreback]

I changed this to make this an enhancement for a simple .to_epoch() method on Timestamp/DTI.

[jbrockmendel]

since timestamp now has timestamp method, should,we use the same name for DTI?

[jreback]

yes this would be reasonable (though to be honest the .timestamp() name is not very informative.....