Despite all my obvious love for NLP and grammars, I would actually like to echo markessien's point here. I agree that NLP might not be the best approach here,

Despite all my obvious love for NLP and grammars, I would actually like to echo markessien's point here. I agree that NLP might not be the best approach here, especially if you're having to learn all of it from scratch (I'm no expert but I learnt enough basics so that I could look into any aspect in more depth when it comes to it). My first suggestion would be to take a step back and think about what the system is and what is the easiest, fastest and most intuitive way to input dates. Brainstorm this and you will come up with good ideas like those above. I like the autocomplete idea and also there's no reason not to use some syntax like "Dentist @ 2pm", i.e. using @ to separate title from date. It's sufficient to indicate to the machine which is text and which is date info, but close enough to natural speech as well (also the @ is a very recognisable character now). One thing to note is that Google Calendar accepts expressions such as "Dentist at 2pm"; perhaps you can try that and see how you like how that works?