If you are keen on birds you tend to note firsts - the first migrant of the year (usually Chiffchaff) then the other early birds such as Sand Martin, Wheatear and Willow Warbler. As the year progresses into summer its less of an issue.
There are some Butterflies which are also notably early. These are the ones that overwinter as an adult. Mostly they are the larger species such as Peacock and Small Tortoiseshell. Another is the Comma (pictured). The Comma is new to our area. For a while it was doing rather badly in the UK however it managed to switch foodplants and has made a spectacular recovery, moving north quickly and now is regularly seen in Central Scotland. The warm Spring day when it appeared it was one of four seen together at the site.