Set type for datetime intervals

[Nagy László Zsolt]

> Sorry to be late to the party--I applaud that you have already 
> crafted something to attack your problem.  When you first posted, 
> there was a library that was tickling my memory, but I could not 
> remember its (simple) name.  It occurred to me this morning, after 
> you posted your new library:
>
>   https://pypi.python.org/pypi/intervaltree
>
> This handles overlapping ranges nicely and provides some tools for 
> managing them.  Before posting this, I checked that it works with 
> datetime types, and, unsurprisingly, it does.
Thank you! It is so much better than the one I have created. Possibly
I'll delete my own module from pypi. :-)