Param types: Ah, of course. I had a vague suspicion that was what was going on. But my brain was overloaded. Yeah, one concept per example is ideal. :-)

'Year' alias: excellent! That's one of those "look and feel" things that can make the transition to a new language so much smoother.

I was going to add something about "now comes the hard part after the initial flurry of activity: steadily growing the language without losing the passion." But I didn't want to end on a downer. I'm truly impressed with what you have so far.