Over a year, I have some daily response $y$ (suicides per day in US). It's data for one year only.
Other than seasons, what time covariate should I include? A month-covariate? A week-covariate? A day-covariate?
I have plotted the data, and cannot see an affect other than the seasons-effect. So, if I am to include the one of the other three possible covariates, which one should it be, and why? How do I "defend" its inclusion given that I can't see any clear effect via plots?