Yea, that would have stumped me, expecting a trick/trap. What if my birthday is tomorrow? By the time my teacher checks it, it's wrong. "Your birth year" would have prevented that.
This is a problem I have with certain parts of computer science and math education. Everything is encouraged to be exact, then, suddenly, variable names are used inconsistently, niche cases are ignored arbitrarily and explained with essentially referring to "common sense".