Haha, nice example! If you want to do this you'd better use our full platform Wit.ai [1], that will arbitrate competition between the datetime entity (`tomorrow at three`) and the number_of_person entity!

[1] https://wit.ai

As a human, without a colon that thing is ambiguous.

It can be:

    tomorrow at three thirty, people are coming over

or: tomorrow at three, thirty people are coming over