> I want to keep this function as a placeholder for a future time when we improve the mechanism

> there is currently no good approach to comparing time units

We don't know if it's the correct solution to a problem we haven't solved yet. What if this function becomes entrenched in the codebase, only for us to discover it was not the correct approach?

We could, for example, decide to manage epochs in ```CubeList.__add__```. Regardless of whether I can imagine an alternative future scenario or not, this function really seems inappropriate for this PR, and I think we should focus on that.