On the date picker, when you click on the date, it brings up a screen that has 3 1/2 years of months making it easier to select a date but the dates start on the current year and go forwards 3 1/2 years.

I can't imagine there would be any requirement to add sightings in the future. At the moment I have to scroll backwards with my mouse wheel which is only a small problem but it would speed the input up, and makes sense, to have the current year and the previous 3 1/2 years to pick from (rather than a future date which will never be picked).