Year is not really a variable since it simply that, a year. The data probably is not normal in distribution either, since your variables would probably occur at similar time of the year. But you can compare first appearance or peak abundance using Chi square tests, which compare actual results against expected :)

Another approach: before you dive into complicated statistics, just visualize your data. This makes it much easier to think about what to look for and what questions to ask. What about having the year on the X-axis and the day of first appearance on the Y-axis? How does the pattern look like? Just random? Or does it look like the days decrease towards the presence? Then, a simple correlation test might be all you need.

Hello Emma; What organism are you studying? A migratory bird? An annual plant? Is emergence a regularly recurrent event? Knowing those things might help us think more exactly about the question. Jim Des Lauriers