I have 25 years of nest initiation dates, I used quantile regression to look for changes in the distribution over time, as well as to look in detail to early and late breeders. My model would be something like: nest date ~ year. Since the environment where the species nest is highly variable, there is a lot of fluctuation in nest initiation dates. Do I need to center my observations (i.e. my response variable laying date) for each year before I run the quantile regression to get rid of the noise of annual variation? (i.e. that some years all birds nest late and other all birds nest early).