I feel you’ve missed the point I was making and assumed I’ve made another. Age number and year number are different. You’re in your first year when your age is not yet 1. You’re in your second year when your age is between 1 and 2.
Years follow numbers as in "this year was the first/second/third year of ", not “this year was the year turned X years old”
See, that’s much closer to “(It was) my pleasure”, which is a valid English response (though these days it puts people in the mind of “Chick-fil-A employee”) than it is “You’re welcome”.