Added hourofyear for pivoting calcualtions
I do not know if this is possible. But very much needed.

AFAIK hoy is not an existing field. We'd love to merge a complete PR if you can implement it and add a test case. 
Thanks for the feedback. Please keep the feature requests/bug reports coming!
 I am just trying to improve the pivoting of time series.

Especially:
#1953

and

#833 (#736)

But I feel quite lost as my array knowledge is limited.
Also:
Where's the source for 

```
import pandas.lib as lib
```

?
 I have now the required function, purely python:

```
def hoy_dtobj64(dt_obj64):
    """
    calculate hour of year for a 'datetime64[ns]' object
    """
    doy = dt_obj64.dayofyear
    second = ((doy-1)*3600*24 + dt_obj64.hour*3600 + 
                dt_obj64.minute*60+dt_obj64.second)
    hoy = (second / 3600) + 1

    return hoy

```

Where shall we place it?

As an additional property of the index?
 You're almost there :)

the definition for Timestamp resides in pandas/src/datetime.pyx
you can add that method in a similar manner as dayofweek/dayofyear etc.

Finally you'll need a few test cases to be added in to pandas/tseries/tests/.
 mmh.

I must admit, I do not understand the code in pandas/src/datetime.pyx

I would need a helping hand.

my pure python function above is much more understandable..
 stalled.
 what means stalled?
 It means "inactive for a long time".
 let's close it then:
#2183
