Halfway to ten.

05:00

This actually makes more sense!

>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...

Well we only disagree 1/60 of the time so it's probably fine as long as we avoid meetings at exactly the half hour.

English thinkers might also want to consider the fact that 0930 is half-way through hour 10

“Halfway to” -> “half”

Yes but it’s uncommon in English to simply drop a word from a sentence while pretty common in German casual discourse.

The only other English common case I can think of is the American “I could [not] care less” dropping “not” which is also confusing.