“Half eleven” may not mean what you think it does.
One of the differences between US and UK English is how we express time. For example, to denote the time “11:30” in the US, you would say, “half past eleven,” whereas in the UK you would simply say “half eleven.” .
This expression, however, can lead to confusion among some, especially German and Dutch speakers for whom the words “half eleven” would clearly indicate “half” of the 11th hour, or 10:30.
Having lived many years in Germany, I almost found myself getting caught in this trap. Luckily, my English friend, who had told me to meet him at “half eleven,” also mentioned the words “eleven thirty” at some point, and then the penny dropped and I realized that I had almost been one hour too early for our appointment.