So currently, this just blanket modifies the resulting string to work in TeX mode, but I wonder if it should be more nuanced and change the formatters for only the numbers?

This seems reasonable, but the tests aren't passing....

Ooops, that's because I set the default to True instead of None.

I am inclined to merge this as-is because people still have the option of specifying the format strings as they wish (and not relying on us to auto-tex-ify them) and we can down down the route of trying to parse the dateformats and decide which should be strings and which are numbers that should be texified when someone asks for it.

Thanks for the nudge - I forgot about this....