>How does one get to "half ten" in German? Is it simply starting from "half to ten"?

Never thought about it much but I think you're spot on. English uses "half past" and therefore "half 10" means 10:30, whereas most other languages use "half to" which causes "half 10" to mean 9:30.

One would think this should cause confusion for international meetings often enough to be common knowledge, but I didn't know until today...