Great points! On one hand I thought it would be nice to hide all those functions from other things that would never need to know about them. On the other hand, this is bad for testing. And if we move them out of here, I also support making them fully functional (arguments in, result out).

My only hesitation was that it seems like a lot of overhead to put every little helper function into its own service (both to define it, and to include it). The other option would be to keep it out of Angular's hands and put it into the `Prometheus.Graph` namespace. Less overhead, but no dependency tracking. Or what about the possibility of having a service that provides an object containing a group of functions (like what `Prometheus.Graph` currently contains), instead of only one. Still relatively little overhead, but at least you are specifying explicitly that you are depending on that group of functions.

Hmm, for now I'll go with the approach of putting all the Graphite time conversion functions into one service, where I make `timestampToGraphiteTime` completely private, so it will only be tested through the public interface (which IMO is often what you should do).