Nice. One thought: why do you call it arrow? I know you can call it anything you want, but one reason requests is so popular because the name totally makes sense. My little 0.2 is why not rename it to pydate or something more intuitive.
What's the difference between .utcnow() and .now()? Is one supposed to be an alias or is .now() default to the time the platform is set to?
I've opened an issue regarding calling convention. What do HNer think?